What does P20F3 SCR NOx Pre- Catalyst Efficiency Below Threshold Bank 2 mean?
P20F3 is a diagnostic trouble code that indicates a problem with the SCR NOx Pre-Catalyst Efficiency Below Threshold for Bank 2 in diesel-powered vehicles.
The powertrain control module has detected that the catalyst efficiency is below the required level for the upstream catalytic converter (or NOx trap) in engine bank two.
Diesel engines produce more harmful exhaust gases, particularly nitrogen oxide (NOx), and SCR systems were developed to reduce these emissions.
The SCR system injects diesel exhaust fluid (DEF) into the exhaust to raise the temperature and improve the efficiency of the catalyst.
If the PCM determines that the catalyst efficiency is insufficient, it will store the P20F3 code and may illuminate the malfunction indicator lamp.
It is important to address this code promptly, as it could lead to catalyst damage.
Possible causes of this code include defective sensors, an inoperative SCR system, incorrect DEF fluid, or exhaust leaks.
Troubleshooting steps should include addressing any other related codes and performing a visual inspection of the SCR injection system, sensors, and wiring.
Diagnostic tools and vehicle-specific information will be necessary to complete a thorough diagnosis.
P20F3 Symptoms
- Excessive black smoke from vehicle exhaust
- Diminished engine performance
- Reduction in fuel efficiency
- Other stored SCR and emission related codes
Possible P20F3 Causes
- Defective O2, NOx, or temperature sensor
- Inoperative SCR system
- Faulty SCR injector
- Incorrect or insufficient DEF fluid
- Bad SCR controller or programming error
- Pre-catalyst exhaust leaks
- Installation of aftermarket or high-performance exhaust components
Troubleshooting P20F3 error code
- Address any other stored SCR or exhaust emissions codes
- Repair any pre-catalyst exhaust leaks
- Perform a visual inspection of the SCR injection system, exhaust temperature sensors, NOx sensors, and oxygen (02) sensor harnesses and connectors
- Repair or replace any burnt or damaged wiring and connectors
- Retrieve all stored codes and freeze frame data
- Clear the codes and test drive the vehicle
- Observe the scanner data stream and compare exhaust sensor data between engine banks
- Test the sensors using a DVOM
- If sensors fail to comply with specifications, consider them defective
- Check the DEF reservoir and ensure it is filled with the appropriate fluid and not contaminated
- If all sensors and circuitry appear to be functioning correctly, suspect a faulty catalyst element or failed SCR system
- Refer to vehicle information for diagnostic flow charts, connector pin out charts, and component testing procedures