Common Error Codes for Diesel Engines

Diesel engines are internal combustion engines that use compression to ignite fuel. Unlike gasoline engines, diesel engines do not use a spark plug to ignite the fuel. Instead, they rely on the high temperature and pressure that is created when the air and fuel are compressed in the cylinder.

Diesel engines are known for their high efficiency and reliability. However, like all mechanical devices, they can still experience problems from time to time. When a problem does occur, it is often indicated by an error code.

There are many different error or fault codes that can be displayed on a diesel engine; in this article, we will take a look at some of the most common ones.

What is a Diagnostic Trouble Code

DTC, or a Diagnostic Trouble Code, is an error code that is generated by the engine control unit (ECU) when it detects a problem. The ECU constantly monitors the engine sensors and systems for any signs of trouble. The ECU will store a DTC in its memory if a problem is detected. This DTC can then be read with a diagnostic tool to help diagnose the problem.

A DTC pinpoints the nature and location of the problem, in contrast to the significant malfunction indicator lamp (MIL), usually referred to as the check engine light, which merely notifies drivers that there is a problem. DTCs, also known as engine vehicle trouble fault codes, may be read with a scanner plugged directly into a car's port.

Drivers and fleet managers may find it useful to have a fundamental grasp of DTCs. Continue reading to find out more about DTCs, how they function, and how to interpret them.

While the acronym DTC may refer to different things in different countries, the meaning is related: it is an error code that is generated by the engine control unit when it detects a problem.

The codes are meant to provide the technician with a hint as to where a defect could be developing within an automobile by identifying a specific issue location. To completely diagnose the issue, it is important to utilize the fault codes in combination with the vehicle's service manual to determine which circuits, systems, or parts need to be examined.

Imagine that a DTC represents an iceberg. The tip of the iceberg is the code, which represents the symptoms that are being shown by the vehicle. However, there is a lot more underneath the surface. The larger part of the iceberg is hidden; to fully understand what is going on, you need to dig deeper.

This is where a service manual or diagnostic tools comes in handy, as it can provide information about the underlying cause of the problem and help guide you to make the repair.

Let us say, for example, a DTC P0420 is displayed. This DTC indicates that there is a problem with the catalytic converter. In order to completely understand what is going on and make the necessary repair, you need to consult the service manual or use diagnostic tools. The service manual will provide information about which circuits, systems, or parts need to be examined in order to troubleshoot the problem.

You will never know exactly what is going on with your vehicle just by looking at the DTC. The fault codes are meant to provide a technician with a starting point for diagnosis, but they will never tell the whole story.

In order to save time, it is important to have a good understanding of how to interpret the fault codes. In the next section, we will look at some of the most common DTCs generated by diesel engines.

Most Common Diagnostic Does & What They Mean

Diesel engines are becoming increasingly popular in a wide range of vehicles, from cars and trucks to boats and RVs. While diesels offer many advantages over gasoline engines—including better fuel economy and increased torque—they can be difficult to diagnose when something goes wrong.

Here are some of the most common diagnostic trouble codes for diesel engines and what they typically mean

Air & Fuel Metering Codes

Air & Fuel Metering fault Codes are the most common diagnostic trouble codes thrown by diesel engines. These fault codes indicate that there is an issue with the way the engine is receiving and measuring air and fuel. The most common causes of these fault codes are a dirty or faulty mass airflow sensor, a dirty or faulty fuel injector, or a problem with the fueling system itself.

When you come across an air & fuel metering code, the first thing you should do is check the mass airflow sensor and the fuel injectors. If they are both clean and working properly, then the next step is to check the fueling system for any leaks or blockages.

Here are some common air & fuel metering fault codes:

P0001: Fuel Volume Regulator Control Circuit/Open

This diagnostic trouble code typically indicates a problem with the fuel related to the volume regulator or its wiring. The fuel volume regulator controls the amount of fuel that is delivered to the engine. If it isn’t working properly, it can cause a lean mixture (too much air and not enough fuel), which can lead to reduced power and fuel economy.

P0002: Fuel Volume Regulator Control Circuit Range/Performance

This diagnostic trouble code typically indicates a problem with the fuel volume regulator or its wiring. If the fuel volume regulator isn’t working properly, it can cause a lean mixture (too much air and not enough fuel), which can lead to reduced power and fuel economy.

P0003: Fuel Volume Regulator Control Circuit Low

This code typically indicates a problem with the fuel volume regulator or its wiring. If the fuel volume regulator isn’t getting enough power, it can cause a rich mixture (too much fuel and not enough air), which can lead to black smoke from the exhaust and possible engine damage.

P0004: Fuel Volume Regulator Control Circuit High

This code typically indicates a problem with the fuel volume regulator or its wiring. If the fuel volume regulator is getting too much power, it can cause an engine misfire.

P0101: Mass or Volume Air Flow Circuit Range/Circuit Performance

This code typically indicates an particular issue with the mass air flow (MAF) sensor or its wiring. The MAF sensor measures the amount of air coming into the engine so that the fuel injectors can deliver the correct amount of fuel. If the MAF sensor isn’t working properly, it can cause a lean mixture (too much air and not enough fuel), which can lead to reduced power and fuel economy.

P0102: Mass or Volume Air Flow Circuit Low Input

This code typically indicates a problem with the MAF sensor or its wiring. If the MAF sensor isn’t getting enough air, it can cause a rich mixture (too much fuel and not enough air), which can lead to black smoke from the exhaust and possible engine damage.

P0103: Mass or Volume Air Flow Circuit High Input

This code typically indicates a problem with the MAF sensor or its wiring. If the MAF sensor is getting too much air, it can cause an engine misfire.

P0200: Fuel Injector Circuit/Open

This code typically indicates a problem with one of the fuel pump injectors or its wiring. If an injector isn’t working properly, it can cause a lean mixture (too much air and not enough fuel pump), which can lead to reduced power and fuel economy.

P0300: Random/Multiple Cylinder Misfire Detected

This code typically indicates a problem with the ignition system. If the spark plugs are fouled or the wires are damaged, it can cause an engine misfire.

P0400: Exhaust Gas Recirculation (EGR) Circuit Malfunction

This code typically indicates a problem with the EGR system. The EGR system recirculates a portion of the exhaust gas back into the engine to help reduce emissions. If the EGR system isn’t working properly, it can cause an engine to misfire and increase emissions.

P0500: Vehicle Speed Sensor (VSS) Circuit Malfunction

This code typically indicates a problem with the VSS or its wiring. The VSS measures the speed of the vehicle so that the transmission can shift properly. If the VSS isn’t working properly, it can cause the transmission to shift erratically or not at all.

P0600: PCM/TCM Serial Communication Error

This code typically indicates a problem with the power train control module (PCM) or transmission control module (TCM). These modules communicate with each other to control the engine and transmission. If they can’t communicate properly, it can cause all sorts of problems, including a no-start condition.

P0700: Transmission Control System (TCS) Malfunction

This code typically indicates a problem with the transmission control system. The TCS is responsible for shifting the transmission. If it isn’t working properly, it can cause the transmission to shift erratically or not at all.

P0800: Transmission Fluid Temperature (TFT) Sensor Circuit Malfunction

This code typically indicates a problem with the TFT sensor or its wiring. The TFT sensor measures the temperature of the transmission fluid. If it isn’t working properly, it can cause the transmission to overheat and fail.

P1000: OBDII Monitor Testing Not Complete

This code typically indicates that the OBDII system hasn’t completed its self-test. The OBDII system is responsible for monitoring the engine and evaporative emission control systems. If it doesn’t complete its self-test, it can’t properly monitor the engine and emission systems.

Auxiliary Emissions Controls

An auxiliary emission control device (AECD) is used to reduce emissions of oxides of nitrogen (NOx) from a diesel engine. The most common AECDs are exhaust gas recirculation (EGR) systems and selective catalytic reduction (SCR) systems in self-test.

EGR systems work by recirculating a portion of the exhaust gas back into the engine cylinders, where it reduces the temperature of the combustion process and therefore reduces the formation of NOx. SCR systems work by injecting a chemical reductant—usually urea—into the exhaust gas, where it reacts with NOx to form harmless nitrogen and water vapor.

P0401: Insufficient EGR Flow

This code indicates that the EGR system is not flowing enough exhaust gas back into the engine. This can be caused by a clogged EGR valve, restricted EGR passages, or a faulty EGR control solenoid.

P0402: Excessive EGR Flow

This code indicates that the EGR system is flowing too much exhaust gas back into the engine. This can be caused by a leaking EGR valve, or an incorrect EGR control solenoid duty cycle.

P0403: Exhaust Gas Recirculation Circuit Malfunction

This code indicates that there is a problem with the EGR control circuit. This can be caused by a faulty EGR control solenoid, an open or short in the EGR control circuit, or a faulty PCM.

P0404: Exhaust Gas Recirculation Circuit Range/Performance

This code indicates that the EGR system is not functioning properly. This can be caused by a clogged EGR valve, restricted EGR passages, a faulty EGR control solenoid, or an incorrect EGR control solenoid duty cycle.

P0405: Exhaust Gas Recirculation Sensor A Circuit Low

This code indicates that the EGR sensor is not reading properly. This can be caused by a faulty EGR sensor, an open or short in the EGR sensor circuit, or a faulty PCM.

P0406: Exhaust Gas Recirculation Sensor A Circuit High

This code indicates that the EGR sensor is not reading properly. This can be caused by a faulty EGR sensor, an open or short in the EGR sensor circuit, or a faulty PCM.

P0407: Exhaust Gas Recirculation Sensor B Circuit Low

This code indicates that the EGR sensor is not reading properly. This can be caused by a faulty EGR sensor, an open or short in the EGR sensor circuit, or a faulty PCM.

P0408: Exhaust Gas Recirculation Sensor B Circuit High

This code indicates that the EGR sensor is not reading properly. This can be caused by a faulty EGR sensor, an open or short in the EGR sensor circuit, or a faulty PCM.

P1400: SCR NOx Conversion Efficiency Below Threshold

This code indicates that the SCR system is not converting NOx into harmless nitrogen and water vapor efficiently. This can be caused by a faulty SCR catalyst, a restricted SCR exhaust filter, or a problem with the urea dosing system.

P1401: SCR Temperature Below Threshold

This code indicates that the SCR system is not operating at the proper temperature. This can be caused by a faulty SCR catalyst, a restricted SCR exhaust filter, or a problem with the urea dosing system.

P1402: Reduction Efficiency Below threshold

This code indicates that the SCR system is not converting NOx into harmless nitrogen and water vapor efficiently. This can be caused by a faulty SCR catalyst, a restricted SCR exhaust filter, or a problem with the urea dosing system.

P1403: Ammonia Slip Below threshold

This code indicates that there is too much ammonia in the SCR system. This can be caused by a faulty SCR catalyst, a restricted SCR exhaust filter, or a problem with the urea dosing system.

P1404: Ammonia Slip Above threshold

This code indicates that there is too much ammonia in the SCR system. This can be caused by a faulty SCR catalyst, a restricted SCR exhaust filter, or a problem with the urea dosing system.

P1405: SCR Inlet NOx Above Threshold

This code indicates that there is too much NOx in the SCR system. This can be caused by a faulty SCR catalyst, a restricted SCR exhaust filter, or a problem with the urea dosing system.

Computer and Auxiliar Outputs

Computer and Auxiliar Outputs comes with a list of diagnostic trouble codes for diesel engines. The computer will display the code when it has been activated by the engine control unit (ECU). It is important to note that these fault codes are only meant to guide technicians in diagnosing and repairing problems with the engine; they are not intended as a substitute for proper training and experience.

The most common fault codes are:

P0087: Fuel Rail/System Pressure Too Low

These fault codes typically indicates that there is a problem with the fuel pressure sensor or the fuel pump. If the fuel pump pressure sensor is faulty, it may not be sending the correct signal to the computer. This can cause the computer to think that the fuel pressure is too low, even when it’s not.

P0088: Fuel Rail/System Pressure Too High

Conversely, this code indicates that the fuel pump pressure is too high. This can be caused by a faulty fuel pump pressure regulator, a leak in the fuel pump system, or a problem with the injectors.

P0089: Fuel Pressure Regulator 1 Performance

This code is related to P0087 and P0088, but it specifically refers to the fuel pump pressure regulator. A defective regulator can cause low or high fuel pump pressure, depending on how it fails.

P0106: Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem

This code indicates that there is a problem with the MAP sensor. The MAP sensor measures the air pressure inside the intake manifold. If it’s not working correctly, it can cause issues with fuel pump delivery and engine timing.

P0107: Manifold Absolute Pressure/Barometric Pressure Circuit Low Input

This code is related to P0106, but it specifically refers to a low input from the MAP sensor. This can be caused by a faulty MAP sensor, a loose connection, or a vacuum leak in the intake manifold.

P0108: Manifold Absolute Pressure/Barometric Pressure Circuit High Input

Again, this code is related to P0106 and P0107, but it refers to a high input from the MAP sensor. A high input can be caused by a defective MAP sensor, an electrical short, or a problem with the computer.

P0191: Fuel Rail Pressure Sensor Circuit Range/Performance

This code indicates that there is a problem with the fuel pump rail pressure sensor. The fuel pump rail pressure sensor measures the pressure of the fuel in the fuel injectors. If it’s not working correctly, it can cause issues with fuel pump delivery and engine timing.

P0192: Fuel Rail Pressure Sensor Circuit Low Input

This code is related to P0191, but it specifically refers to a low input from the fuel rail pressure sensor. This can be caused by a faulty sensor, a loose connection, or a problem with the computer.

P0193: Fuel Rail Pressure Sensor Circuit High Input

Again, this code is related to P0191 and P0192, but it refers to a high input from the fuel pump pressure sensor. A high input can be caused by a defective sensor, an electrical short, or a problem with the computer.

P0216: Injection Timing Control Circuit/Open

This code indicates that there is a particular issue with the injection timing control circuit. This can be caused by a problem with the computer, a faulty sensor, or a problem with the injectors.

P0217: Injection Timing Control Circuit Low

This code is related to P0216, but it specifically refers to a low signal from the injection timing control circuit. This can be caused by a problem with the computer, a faulty sensor, or a problem with the injectors.

P0218: Injection Timing Control Circuit High

Again, this code is related to P0216 and P0217, but it refers to a high signal from the injection timing control circuit. This can be caused by a problem with the computer, a faulty sensor, or a problem with the injectors.

P0299: Turbo/Supercharger Underboost

This code indicates that the turbochargers or supercharger is not providing enough boost. This can be caused by a problem with the turbochargers, a leak in the intake or exhaust system, or a problem with the computer.

P0300: Random/Multiple Cylinder Misfire Detected

This code indicates that there is an issue with one or more of the cylinders. This can be caused by a problem with the injectors, a problem with the ignition system, or a problem with the computer.

P0301: Cylinder 1 Misfire Detected

This code is related to P0300, but it specifically refers to cylinder 1. This can be caused by a problem with the injector, a problem with the ignition system, or a problem with the computer.

P0302: Cylinder 2 Misfire Detected

Again, this code is related to P0300 and P0301, but it specifically refers to cylinder 2. This can be caused by a problem with the injector, a problem with the ignition system, or a problem with the computer.

P0600: Serial Communication Link Malfunction

This code indicates that there is a problem with the serial communication link. This can be caused by a self-test problem with the computer, a loose connection, or an electrical short.

P0601: Internal Memory Checksum Error

This code indicates that there is a problem with the computer’s memory. This can be caused by a problem with the computer, a loose connection, or an electrical short.

P0602: Control Module Programming Error

This code indicates that there is a problem with the computer’s programming. This can be caused by a problem with the computer, a loose connection, or an electrical short.

P0603: Internal Keep Alive Memory Error

This code indicates that there is a problem with the computer’s keep alive memory. This can be caused by a problem with the computer, a loose connection, or an electrical short.

P0622: Generator Field Control Circuit

This code indicates that there is a problem with the generator field control circuit. This can be caused by a problem with the generator, a loose connection, or an electrical short.

P0623: Generator Field/Exciter Circuit Voltage Regulator

This code indicates that there is a problem with the generator field/exciter circuit low voltage regulator. This can be caused by a problem with the generator, a loose connection, or an electrical short.

P0642: Sensor Reference Voltage "A" Circuit Low

This code indicates that there is a problem with the sensor reference low voltage “A” circuit. This can be caused by a problem with the sensor, a loose connection, or an electrical short.

P0643: Sensor Reference Voltage "A" Circuit High

This code is related to P0642, but it specifically refers to a high voltage in the sensor reference voltage “A” circuit. This can be caused by a problem with the sensor, an electrical short, or a problem with the computer.

P0652: Sensor Reference Voltage "B" Circuit Low

This code indicates that there is a problem with the sensor reference low voltage “B” circuit. This can be caused by a problem with the sensor, a loose connection, or an electrical short.

P0656: Fuel Level Output Circuit Malfunction

This code indicates that there is a problem with the fuel pump level output circuit. This can be caused by a problem with the sensor, a loose connection, or an electrical short.

P0657: Fuel Level Output Circuit Low

This code is related to P0656, but it specifically refers to a low voltage in the fuel level output circuit. This can be caused by a problem with the sensor, a loose connection, or an electrical short.

Ignition System

Your diesel engine won't start, or it starts then dies, if the ignition system isn't working correctly. Common problems include:

P0016: Crankshaft/Camshaft Timing Misalignment

This diagnostic trouble fault code indicates that the timing belt or chain connecting the crankshaft to the camshaft(s) has skipped a tooth or two, resulting in improper valve timing. This can cause a number of problems, including decreased fuel economy, increased emissions, and reduced power.

P0087: Fuel Rail/System Pressure Too Low

This fault code indicates that the self-test fuel pump pressure in the fuel pump rail is too low. This can be caused by a number of things, including a faulty fuel pump, clogged fuel filter, or leak in the fuel pump system.

P0088: Fuel Rail/System Pressure Too High

This diagnostic trouble fault code indicates that the fuel pump pressure in the fuel rail is too high. This can be caused by a number of things, including a faulty fuel pump pressure regulator, leaking injectors, or a restricted fuel return line.

P0093: Fuel Leak Detected in the High-Pressure System

This code indicates that there is a leak in the high-pressure side of the fuel system. This can be caused by a number of things, including a faulty injector, leaking fuel lines, or a loose connection.

P0300: Random/Multiple Cylinder Misfire Detected

This code indicates that there is a misfire in one or more of the cylinders. This can be caused by a number of things, including a faulty injector, dirty fuel filter, low fuel pressure, or restricted air intake.

P0301-3122: Cylinder 1 Misfire Detected

This fault code indicates that there is a misfire in cylinder 1-12. This can be caused by a number of things, including a faulty injector, dirty fuel filter, low fuel pressure, or restricted air intake.

P0320: Ignition/Distributor Engine Speed Input Circuit Signal Malfunction

This fault code indicates that there is a problem with the signal from the distributor to the ignition system. This can be caused by a number of things, including a faulty distributor, ignition coil, or spark plug.

P0322: Ignition/Distributor Engine Speed Input Circuit No Signal

This fault code indicates that there is no signal from the distributor to the ignition system. This can be caused by a number of things, including a faulty distributor, ignition coil, or spark plug.

P0401: Exhaust Gas Recirculation (EGR) Flow Insufficient

This fault code indicates that the EGR system is not flowing enough exhaust gas back into the engine. This can be caused by a number of things, including a faulty EGR valve, EGR cooler, or EGR gasket.

P0402: Exhaust Gas Recirculation (EGR) Flow Excessive

This code indicates that the EGR system is flowing too much exhaust gas back into the engine. This can be caused by a number of things, including a faulty EGR valve, EGR cooler, or EGR gasket.

P0403: Exhaust Gas Recirculation (EGR) Circuit Malfunction

This code indicates that there is a problem with the EGR system circuit. This can be caused by a number of things, including a faulty EGR valve, EGR sensor, or wiring harness.

P0404: Exhaust Gas Recirculation (EGR) Position Sensor Circuit Range/Performance

This diagnostic trouble code indicates that the EGR position sensor is not working properly. This can be caused by a number of things, including a faulty EGR valve, EGR sensor, or wiring harness.

P0335: Crankshaft Position Sensor A Circuit Malfunction

This fault code indicates that there is a problem with the crankshaft position sensor circuit. This can be caused by a number of things, including a faulty crankshaft position sensor, wiring harness, or ECM.

P0336: Crankshaft Position Sensor A Circuit Range/Performance

This code indicates that the crankshaft position sensor is not working properly. This can be caused by a number of things, including a faulty crankshaft position sensor, wiring harness, or ECM.

P0420: Catalyst System Efficiency Below Threshold

This code indicates that the catalytic converter is not working properly. This can be caused by a number of things, including a faulty catalytic converter, oxygen sensor, or exhaust gas recirculation system.

P0430: Catalyst System Efficiency Below Threshold (Bank 2)

This code indicates that the catalytic converter on bank 2 is not working properly. This can be caused by a number of things, including a faulty catalytic converter, oxygen sensor, or exhaust gas recirculation system.

P0350: Ignition Coil Primary/Secondary Circuit Malfunction

This diagnostic trouble code indicates that there is a problem with the ignition coil circuit. This can be caused by a number of things, including a faulty ignition coil, spark plug, or wiring harness.

Vehicle Speed, Idle Control, and Auxiliary Inputs

P0087: Fuel PUMP Rail/System Pressure Too Low

This code typically indicates a problem with the fuel pump or fuel pressure regulator. It can also be caused by a leaking injector or fuel pump pressure leak.

P0088: Fuel Rail/System Pressure Too High

This fault code usually means there is a problem with the high-pressure side of the fuel system, such as a blocked fuel pump filter or restricted fuel pump return line. It can also indicate an issue with the fuel pump pressure regulator or a leaking injector.

P0089: Fuel Pressure Regulator 1 Performance

This code indicates that the fuel pressure regulator is not working properly. It could be caused by a sticking valve, dirty filter, or restricted fuel return line.

P0106: Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem

This diagnostic trouble code typically means there is an issue with the MAP sensor or its circuit. It could also be caused by a leaking intake manifold gasket or a faulty vacuum leak.

P0107: Manifold Absolute Pressure/Barometric Pressure Circuit Low Input

This code indicates that the MAP sensor is not reading correctly. It could be caused by a loose connection, dirty sensor, or faulty circuit.

P0108: Manifold Absolute Pressure/Barometric Pressure Circuit High Input

This code means that the MAP sensor is reading too high. It could be caused by a faulty sensor or a short in the MAP sensor circuit.

P0122: Throttle Position Sensor/Switch A Circuit Low Input

This code indicates that the TPS sensor is not reading correctly. It could be caused by a loose connection, dirty sensor, or faulty circuit.

P0500: Vehicle Speed Sensor Malfunction

This diagnostic trouble code means that there is an issue with the vehicle speed sensor. It could be caused by a faulty sensor or a problem in the circuit.

P0505: Idle Control System Malfunction

This code indicates that there is an issue with the idle control system. It could be caused by a dirty throttle body, sticking IAC valve, or faulty ECM.

P0600: Serial Communication Link Malfunction

This code means that there is a problem with the communication between the ECM and other modules. It could be caused by a loose connection, bad ground, or faulty wiring.

P0601: Internal Control Module Memory Check Sum Error

This code indicates that there is an issue with the ECM. It could be caused by a faulty ECM or corrupted data.

P0602: Control Module Programming Error

This code means that there is an issue with the ECM programming. It could be caused by a faulty ECM or incorrect software.

P1693: Fuel Injector Circuit Malfunction - Cylinder 3

This code indicates that there is an issue with the fuel pump injector circuit for cylinder 3. It could be caused by a faulty injector, short in the circuit, or open in the circuit.

P0520: Engine Oil Pressure Sensor/Switch Circuit Malfunction

This code means that there is an issue with the engine oil pressure sensor or circuit. It could be caused by a faulty sensor, short in the circuit, or open in the circuit.

P0530: A/C Refrigerant Pressure Sensor Circuit Malfunction

This code means that there is an issue with the A/C refrigerant pressure sensor or circuit. It could be caused by a faulty sensor, short in the circuit, or open in the circuit.

P0534: Air Conditioner Refrigerant Charge Loss

This code indicates that there is a problem with the A/C system. It could be caused by a leaking hose, damaged compressor, or low refrigerant levels.

P0550: Power Steering Pressure Sensor Circuit Malfunction

This code means that there is an issue with the power steering pressure sensor or circuit. It could be caused by a faulty sensor, short in the circuit, or open in the circuit.

P0606: Control Module Processor Fault

This code indicates that there is an issue with the ECM. It could be caused by a faulty ECM or corrupted data.

P0560: System Voltage Malfunction

This code means that there is an issue with the system voltage. It could be caused by a bad battery, loose connection, or faulty alternator.

P0622: Generator Field Control Circuit Malfunction

This code indicates that there is an issue with the generator field control circuit. It could be caused by a faulty connection, open in the circuit, or short to ground.

P0565: Cruise Control On Signal Malfunction

This code means that there is an issue with the cruise control on signal. It could be caused by a faulty switch, loose connection, or open in the circuit.

P0570: Cruise Control Accel Signal Malfunction

This code means that there is an issue with the cruise control accel signal. It could be caused by a faulty switch, loose connection, or open in the circuit.

P0605: Internal Control Module Read Only Memory Error

This code indicates that there is an issue with the ECM. It could be caused by a faulty ECM or corrupted data.

P0603: Internal Control Module Keep Alive Memory Error

This code indicates that there is an issue with the ECM. It could be caused by a faulty ECM or corrupted data.

P0610: Internal Control Module Fault

This code indicates that there is an issue with the ECM. It could be caused by a faulty ECM or corrupted data.

P0611: Fuel Injector Control Module Performance

This code means that there is an issue with the fuel pump injector control module. It could be caused by a faulty module, loose connection, or open in the circuit.

Other Codes

P0700: Transmission Control System Malfunction

The P0700 code indicates that the transmission control system (TCS) has found a problem. It's important to remember that this is a generic powertrain code, which means it covers all makes/models, 1996 and newer. When the TCS engine light comes on, it means that there is a problem with the shift solenoids or the pressure sensors.

P0703: Torque Converter/Brake Switch B Circuit Malfunction

The P0703 code indicates that the torque converter/brake switch B circuit is malfunctioning. This can be caused by a faulty solenoid, an open in the circuit, or a short in the circuit.

P0704: Clutch Pedal Position Sensor Circuit Malfunction

The P0704 code indicates that the clutch pedal position sensor circuit is malfunctioning. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0705: Transmission Range Sensor Circuit Malfunction (PRNDL Input)

The P0705 code indicates that the transmission range sensor circuit is malfunctioning. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0706: Transmission Range Sensor Circuit Range/Performance

The P0706 code indicates that the transmission range sensor circuit is not functioning properly. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0707: Transmission Range Sensor Circuit Low Input

The P0707 code indicates that the transmission range sensor circuit has a low input. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0708: Transmission Range Sensor Circuit High Input

The P0708 code indicates that the transmission range sensor circuit has a high input. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0713: Transmission Fluid Temperature Sensor Circuit High Input

The P0713 code indicates that the transmission fluid temperature sensor circuit has a high input. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0714: Transmission Fluid Temperature Sensor Circuit Low Input

The P0714 code indicates that the transmission fluid temperature sensor circuit has a low input. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0715: Input/Turbine Speed Sensor Circuit Malfunction

The P0715 code indicates that the input/turbine speed sensor circuit is malfunctioning. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0716: Output/Speed Sensor Circuit No Signal

The P0716 code indicates that the output/speed sensor circuit is not providing a signal. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0717: Input/Turbine Speed Sensor Circuit No Signal

The P0717 code indicates that the input/turbine speed sensor circuit is not providing a signal. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0720: Output Shaft Speed Sensor Circuit Malfunction

The P0720 code indicates that the output shaft speed sensor circuit is malfunctioning. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0721: Output Shaft Speed Sensor Circuit Range/Performance

The P0721 code indicates that the output shaft speed sensor circuit is not functioning properly. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0722: Output Shaft Speed Sensor Circuit No Signal

The P0722 code indicates that the output shaft speed sensor circuit is not providing a signal. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0723: Torque Converter/Brake Switch B Circuit High

The P0723 code indicates that the torque converter/brake switch B circuit is high. This can be caused by a faulty solenoid, an open in the circuit, or a short in the circuit.

P0724: Torque Converter/Brake Switch B Circuit Intermittent

The P0724 code indicates that the torque converter/brake switch B circuit is intermittent. This can be caused by a faulty solenoid, an open in the circuit, or a short in the circuit.

P0725: Engine Speed Input Circuit Malfunction

The P0725 code indicates that the engine speed input circuit is malfunctioning. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0726: Engine Speed Input Circuit Range/Performance

The P0726 code indicates that the engine speed input circuit is not functioning properly. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0727: Engine Speed Input Circuit No Signal

The P0727 code indicates that the engine speed input circuit is not providing a signal. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0728: Transmission Fluid Pressure Sensor/Switch "A" Circuit Low

The P0728 code indicates that the transmission fluid pressure sensor/switch "A" circuit is low. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0729: Transmission Fluid Pressure Sensor/Switch "A" Circuit High

The P0729 code indicates that the transmission fluid pressure sensor/switch "A" circuit is high. This can be caused by a faulty sensor, an open in the circuit, or a short in the circuit.

P0730: Incorrect Gear Ratio

The P0730 code indicates that the transmission is in the wrong gear. This can be caused by a faulty shift solenoid, an open in the circuit, or a short in the circuit.

P0731: Gear 1 Incorrect Ratio

The P0731 code indicates that the transmission is in gear 1 but the engine speed is too high for that gear. This can be caused by a faulty shift solenoid, an open in the circuit, or a short in the circuit.

P0732: Gear 2 Incorrect Ratio

The P0732 code indicates that the transmission is in gear 2 but the engine speed is too high for that gear. This can be caused by a faulty shift solenoid, an open in the circuit, or a short in the circuit.

P0733: Gear 3 Incorrect Ratio

The P0733 code indicates that the transmission is in gear 3 but the engine speed is too high for that gear. This can be caused by a faulty shift solenoid, an open in the circuit, or a short in the circuit.

P0734: Gear 4 Incorrect Ratio

The P0734 code indicates that the transmission is in gear 4 but the engine speed is too high for that gear. This can be caused by a faulty shift solenoid, an open in the circuit, or a short in the circuit.

P0735: Gear 5 Incorrect Ratio

The P0735 code indicates that the transmission is in gear 5 but the engine speed is too high for that gear. This can be caused by a faulty shift solenoid, an open in the circuit, or a short in the circuit.

P0736: Reverse Incorrect Ratio

The P0736 code indicates that the transmission is in reverse but the engine speed is too high for that gear. This can be caused by a faulty shift solenoid, an open in the circuit, or a short in the circuit.

P0740: Torque Converter Clutch Circuit Malfunction

The P0740 code indicates that the torque converter clutch circuit is malfunctioning. This can be caused by a faulty solenoid, an open in the circuit, or a short in the circuit.

P0741: Torque Converter Clutch Circuit Performance or Stuck Off

The P0741 code indicates that the torque converter clutch circuit is not functioning properly or is stuck in the off position. This can be caused by a faulty solenoid, an open in the circuit, or a short in the circuit.

P0742: Torque Converter Clutch Circuit Stuck On

The P0742 code indicates that the torque converter clutch circuit is stuck in the on position. This can be caused by a faulty solenoid, an open in the circuit, or a short in the circuit.

You may notice that most of these fault codes start with "P", however, there are other fault codes that start with different letters. Here are some of the examples:

• C1091: Speed Wheel Sensor All Coherency Failure

• C1095: Speed Wheel Sensor 1 Coherency Failure

• C1096: Speed Wheel Sensor 2 Coherency Failure

• C1104: Traction Control Active Lamp – Circuit Short to Battery

• C1105: Traction Control Active Lamp – Circuit Open

• C1287: Booster Pedal Force switch circuit Failure

• C1288: Pressure Transducer Main / Primary Input Circuit Failure

• C1289: Pressure Transducer Redundant / Secondary Input Circuit Failure

• C1400: Traction Control Valve RF Circuit Failure

• B1004: EEPROM Configuration Checksum Error

• B1005: Injector Balance Pressure Sensor Circuit Fault Codes

• U1041: Loss of Class 2 Serial Data to PCM

• B1248: Passenger’s Seatback Autoglide Rearward Switch Circuit Short to Ground

• B1249: Blend Door Failure

• B1250: Air Temperature Internal Sensor Circuit Failure

• B1251: Air Temperature Inlet Sensor Circuit Failure

• B1252: Ambient Air Pressure Sensor Circuit Open or Shorted to Ground

• U1255: Loss of Serial Data from Driver Seat Position Sensor

• U2016: Signal Link Short to Ground (Non SCP) / From NGV Module

• U2017: Driver Side Crash Sensor Communication Fault (Non SCP)

• U2018: Passenger Side Crash Sensor Communication Fault (Non SCP)

• U2019: Audio Voice Module Not Responding Fault Codes

• U2020: Audio Center Amp is not responding

• U2021: Invalid /fault data received (Non SCP)

• U2150: SCP (J1850) Invalid Data from REM

• U2151: SCP (J1850) No Data from REM

• U2152: SCP (J1850) Invalid or Missing Data for Tire Pressure Monitor

• U2401: Lost Communication with Transmission Control Module

• U2402: Lost Communication with Transfer Case Control Module

• U2403: Lost Communication with Gear Shift Module

• U2404: Lost Communication with Park Brake Control Module

• U2405: Lost Communication with Anti-Lock Brake System (ABS) Control Module

Shop Diesel Engine Parts at Heavy Duty Pros

Heavy Duty Pros is your one-stop shop for all your diesel engine parts needs. We carry a wide selection of parts for all makes and models of diesel engines, including common diagnostic trouble codes.

We have Caterpillar Engine Rebuild Kits that fit the 3116, 3126, and C7 Caterpillar engines. These engines for Caterpillar are used in a wide variety of applications, including on-highway trucks, construction equipment, agricultural equipment, and more.

We also have Detroit Diesel DD15 engine parts for sale. The DD15 is a turbocharged diesel engine that is used in many Freightliner trucks. It is also used in some models of the Western Star, Sterling, and Thomas Built Buses.

If you're looking for Cummins diesel engine parts , we carry those too! These Cummins Engine Rebuild Kits fit the 5.9L and 6.7L Dodge Cummins engines.

Lastly, we also offer Navistar Engine Rebuild Kits . These fit the Maxxforce 7, 9, and 10 engines that are used in many International trucks.

No matter what type of diesel engine you have, Heavy Duty Pros has the parts you need to keep it running smoothly. And if you run into any problems, our team is always here to help. Just give us a call or chat with us online, and we'll be happy to assist you.

Diesel engines are built to last, but they do require regular maintenance in order to keep them running smoothly. That's where we come in! We have a wide selection of diesel engine parts for all your needs, including common diagnostic trouble codes.

If you're experiencing any problems with your diesel engine, the first step is to check for diagnostic trouble codes. These fault codes can help you identify the issue and narrow down the possible causes.