How severe is this DTC?
A stored P20BA code should be considered severe and addressed as soon as possible. The SCR system may 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 P20BA fault code may include:
- Decreased engine performance
- Excessive black smoke from the vehicle’s exhaust
- Reduced fuel efficiency
- Other SCR-related codes
What are some common causes of the code?
Causes
of this code may include:
- Faulty reductant heater
- Open or shorted circuits in the reductant heater control
- Defective reductant temperature sensor
- Faulty SCR controller/PCM or programming error
What are the troubleshooting steps for P20BA?
You will need access to a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle-specific diagnostic information to diagnose a P20BA code.
If you can find a technical service bulletin (TSB) that matches the vehicle’s year, make, and model; as well as the 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’s wiring 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 flowcharts, connector pinout diagrams, connector face views, as well as 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’s power supply. Test fuses with the circuit loaded to avoid misdiagnosis. If proper power (battery voltage) and ground circuits are found, use the scanner to activate the reductant heater(s) and test the output control circuit voltage. If voltage is insufficient, suspect the controller is faulty or has encountered a programming error.
If the output voltage circuit is within parameters, use the DVOM to test the reductant heater element in question. If the heater does not meet manufacturer specifications, suspect it has failed.
If this code appears in warm weather, suspect a programming error has occurred…