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P2038 Reductant Injection Air Pressure Sensor A Circuit Range/Performance

OBD-II Trouble Code Technical Description

Article by
Stephen Darby
Stephen Darby
ASE Certified Technician

Reductant Injection Air Pressure Sensor A Circuit Range/Performance

What does that mean?

This diagnostic trouble code (DTC) is a generic powertrain code and applies to many OBD-II vehicles (1996-newer). That may include but is not limited to vehicles from BMW, Mercedes-Benz, Dodge, Sprinter, etc. Although generic, the exact repair steps may vary depending on year, make, model and powertrain configuration.


 

A stored code P2038 means that the powertrain control module (PCM) has detected a degree of voltage in the reductant injection air pressure sensor A circuit that is outside the normal range.Refer to a model specific service manual to determine which is the "A" circuit.

The catalyst system is responsible for reduction of (basically) all exhaust emissions although certain applications are also equipped with a NOx trap.

总裁俱乐部appExhaust gas recirculation (EGR) systems go another step further in the reduction of NOx. Nevertheless, today's larger and more powerful diesel engines cannot meet strict federal (U.S.) emission standards with the EGR, diesel particulate filter/catalytic converter, and NOx trap alone. It was for this reason that selective catalytic reduction (SCR) systems were invented.

总裁俱乐部appSCR systems inject a reductant compound or a diesel exhaust fluid (DEF) into the exhaust in front of the diesel particulate filter, NOx trap, and/or the catalytic converter via the reductant injection valve (solenoid). The precisely timed DEF injection elevates the temperature of the filtration element and allows it to perform more efficiently. It enhances filtration element longevity and allows fewer harmful exhaust emissions to be released into the atmosphere. The entire SCR system is monitored and controlled by either the PCM or a stand-alone controller (which interacts with the PCM). Either way, the controller monitors the O2, NOx, and exhaust temperature sensors (as well as other inputs) to determine the appropriate time for DEF (reductant) injection. Precise DEF injection is necessary to maintain exhaust temperature within acceptable parameters and optimize pollutant filtration.

总裁俱乐部appThe reductant/regeneration supply pump is used to pressurize the DEF in the liquid reductant system for use, when required. Supply pump voltage is monitored by the PCM for consistent fluctuation and load percentage. The PCM also monitors one or more pressure sensors in the reductant supply system to determine if there is a leak in the system.

If the PCM detects a degree of voltage in the reductant injection air pressure sensor A circuit that is outside the normal range, a code P2038 will be stored and a malfunction indicator lamp (MIL) may be illuminated. Multiple ignition cycles - with a failure - may be required for MIL illumination.


P2038

What is the severity of this DTC?

A stored code P2038 should be considered severe and addressed as quickly as possible. The SCR system could be disabled because of it. Catalyst damage could result if the conditions which contributed to the code being stored are not rectified in a timely fashion.

What are some of the symptoms of the code?

总裁俱乐部appSymptoms of a P2038 trouble code may include:

What are some of the common causes of the code?

Causes for this code may include:

What are some P2038 troubleshooting steps?

Make sure that the reductant/regeneration supply system is not losing pressure (internally or externally). Activate the pump to create pressure and inspect the system for external leaks. Use a fuel pressure tester to monitor reductant system pressure manually. Check the supply pump and the injector for leakage. If leaks are discovered (internal or external), they must be repaired before continuing with the diagnosis.

A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle specific diagnostic information will be required to diagnose a code P2038.

总裁俱乐部appYou may use your source of vehicle information to locate a technical service bulletin (TSB) that matches the vehicle year, make, and model; as well as the engine size, code/s stored, and symptoms exhibited. If you find one, it could yield helpful diagnostic information.

Use the scanner (connected to the vehicle diagnostic connector) to retrieve all stored codes and pertinent freeze frame data. It is a good idea to write this information down before clearing the codes then test-drive the vehicle until the PCM either enters readiness mode or the code is reset.

If the PCM enters readiness mode at this time, the code is intermittent and may be much more difficult to diagnose. If this is the case, the conditions which contributed to the code being stored may need to worsen before an accurate diagnosis can be made.

If the code is immediately reset, the next step of your diagnosis will require that you search your vehicle information source for diagnostic flow-charts, connector pin-out charts, connector face views, and component testing procedures/specifications.

Step 1

Use the DVOM to test reductant injection system pressure sensors according to manufacturer specifications. Components which do not test within maximum allowable parameters should be considered defective.

Step 2

If the reductant injection pressure is within specifications, the code P2038 persists, and the sensor in question is in working order, use the DVOM to test input and output signal circuits between sensors and the PCM/SCR controller. Disconnect all controllers prior to using the DVOM for testing.

Related DTC Discussions

Need more help with a P2038 code?

If you still need help regarding the P2038 trouble code, please post your question in our FREE car repair forums.

NOTE: This information is presented for information purposes only. It is not intended as repair advice and we are not responsible for any actions you take on any vehicle. All information on this site is copyright protected.

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