How severe is this DTC?
All stored SCR-related codes can trigger the SCR system shutdown. The stored code P20F0 should be considered severe and addressed as quickly as possible. Catalyst damage could occur if the code is not corrected promptly.
What are some symptoms of the code?
Symptoms of a P20F0 fault code may include:
- Excessive black smoke from the vehicle’s exhaust
- Decreased engine performance
- Reduced fuel efficiency
- Other stored SCR and emission-related codes
What are some common causes of the code?
Causes
of this code may include:
- Faulty exhaust temperature sensor
- Inoperative SCR system
- Defective SCR injector
- Incorrect or insufficient DEF fluid
- Incorrect SCR controller or programming error
- Pre-catalyst exhaust leaks
- Installation of aftermarket or high-performance exhaust parts
What are the troubleshooting steps for P20F0?
If other SCR or exhaust emission codes or exhaust temperature codes are stored, these should be addressed before attempting to diagnose the stored P20F0.
All pre-catalyst exhaust leaks must be repaired before attempting diagnosis for this type of code.
Access to a diagnostic scanner, digital volt/ohmmeter (DVOM), infrared thermometer with laser pointer, and vehicle-specific SCR system diagnostic information source will be necessary to diagnose a P20F0 code.
Finding a technical service bulletin (TSB) that matches the vehicle’s year, make, and model; as well as engine size, stored codes, and presented symptoms could provide useful diagnostic information.
Begin your diagnosis with a visual inspection of the SCR injection system, exhaust temperature sensors, NOx sensors, and oxygen sensor (O2) harnesses and connectors. Burned or damaged wiring and/or connectors should be repaired or replaced before continuing.
Continue by locating the vehicle’s diagnostic connector and connecting the scanner. Retrieve all stored codes and relevant freeze frame data and 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, the code is intermittent and may be much more difficult to diagnose at this point. The conditions that contributed to the code storage may need to worsen before a diagnosis can be reached.
If the code resets immediately, 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 steps of your diagnosis.
Observe the scanner data stream to compare exhaust temperature sensor data (pre and post cat) between engine banks. If inconsistencies are detected, test the exhaust temperature sensors using the DVOM. Sensors that do not meet manufacturer specifications should be considered faulty.
If all sensors and circuits appear to be functioning as expected, suspect that the catalyst element is defective or the SCR system has failed.
Ensure the DEF tank is filled with the appropriate fluid and has not been contaminated in any way