How serious is this DTC?
A stored P2056 code should be considered serious and addressed as quickly 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 P2056 trouble code may include:
- Decreased engine performance
- Excessive black smoke from vehicle exhaust
- Reduced fuel efficiency
- Other SCR-related codes
What are some common causes of the code?
Causes
of this code may include:
- Faulty reductant injector valve
- Open or shorted circuits in reductant injector valve control
- Insufficient DEF in tank
- Faulty SCR controller/PCM or programming error
What are the troubleshooting steps for P2056?
You will need access to a diagnostic scanner, digital volt/ohmmeter (DVOM), and vehicle-specific diagnostic information source to diagnose a P2056 code.
If you can find a technical service bulletin (TSB) that matches the vehicle’s year, make and model; plus engine size, stored code/s and presented symptoms, it could provide helpful diagnostic information.
You’ll want to start your diagnosis with a visual inspection of the reductant heater system harnesses and connectors. Burned or damaged wiring and/or connectors should be repaired or replaced before continuing.
Proceed by hooking up the scanner to the vehicle’s diagnostic connector and retrieving all stored codes and relevant freeze frame data. Note this information before clearing the codes and test drive the vehicle until the PCM enters readiness mode or the code resets.
The code is intermittent and may be much harder to diagnose (for the time being), if the PCM enters readiness mode. 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 resets, consult your vehicle information source for diagnostic flow charts, connector pinout diagrams, connector face views, along with component testing procedures and specifications. This information will be needed to complete the next step of your diagnosis.
Use the DVOM to test the SCR control system power supply. Test fuses with the circuit loaded to avoid misdiagnosis. If proper power and ground circuits are detected, use the scanner to activate the reductant injector valve (solenoid) and test the output control circuit voltage. If voltage is insufficient, suspect the controller is faulty or encountered a programming error.
If the voltage output circuit is within parameters, use the DVOM to test the reductant injector valve in question. If the valve doesn’t meet manufacturer specifications, suspect it has failed.
The reductant injector valve is actually a solenoid injector that sprays reductant fluid into the exhaust