How serious is this DTC?
A stored P2040 code should be considered serious and addressed as soon as possible. The SCR system could be disabled because of this. Catalyst damage could occur if the conditions that contributed to the code being stored are not corrected in a timely manner.
What are some of the symptoms of the code?
Symptoms of a P2040 trouble code may include:
- Reduced fuel efficiency
- Excessive black smoke from the vehicle’s exhaust
- Decreased engine performance
- Other SCR-related codes
What are some common causes of the code?
Causes of this code may include:
- Faulty reductant air pressure sensor (A)
- Open or shorted circuits in the reductant injection air pressure sensor system
- Faulty SCR controller/PCM or programming error
What are the troubleshooting steps for P2040?
Ensure the reductant supply/regeneration 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 manually monitor reductant system pressure. Check the supply pump and injector for leaks. If leaks are discovered (internal or external), they must be repaired before continuing diagnosis.
A diagnostic scanner, digital volt/ohmmeter (DVOM), and vehicle-specific diagnostic information source will be needed to diagnose a P2040 code.
You can use your vehicle information source to locate a technical service bulletin (TSB) that matches the vehicle’s year, make, and model; as well as engine size, stored codes, and presented symptoms. If you find one, it might provide helpful diagnostic information.
Use the scanner (connected to the vehicle’s diagnostic connector) to retrieve all stored codes and relevant freeze frame data. It’s a good idea to record this information before clearing the codes, then test drive the vehicle until the PCM enters readiness mode or the code resets.
If the PCM enters readiness mode at that point, the code is intermittent and may be much more difficult to diagnose. If this is the case, the conditions that contributed to the code being stored may need to worsen before an accurate diagnosis can be made.
If the code immediately resets, the next step in your diagnosis will require you to search your vehicle information source for diagnostic flowcharts, connector pinout diagrams, connector face views, and component testing procedures/specifications.
Step 1
Use the DVOM to test the reductant injection system pressure sensors according to manufacturer specifications. Components that don’t test within allowable parameters should be considered faulty.
Step 2
If reductant injection pressure is within specifications, the P2040 code persists, and the sensor in question is operational, use the DVOM to test the input and output signal circuits between the sensors and the PCM/SCR controller. Disconnect all controllers before using the DVOM for testing.
Reductant injector sensor codes are often attributed to internally leaking supply pumps