Post Catalyst Fuel Trim System Too Rich Bank 2
The post-catalytic converter oxygen sensor on Bank 2 has detected a persistently rich exhaust condition, meaning too much fuel relative to air in the exhaust stream. The PCM adjusts fuel trim to compensate, but when these corrections exceed normal limits, the code sets to alert you of a fuel system imbalance.
What You Might Notice
- Decreased fuel economy
- Rough idle or hesitation during acceleration
- Black smoke or soot from exhaust
- Rotten egg smell from exhaust
- Check Engine Light illuminated
Most Common Causes
- 1
Faulty post-catalyst oxygen sensor
The O2 sensor downstream of the catalytic converter on Bank 2 may be failing or producing incorrect voltage signals, causing the PCM to misread exhaust oxygen levels.
- 2
Fuel injector stuck or leaking
A fuel injector on Bank 2 may be stuck open or leaking fuel into the combustion chamber, causing an overly rich condition that the sensor detects.
- 3
Failed or sticking fuel pressure regulator
A faulty fuel pressure regulator can cause excessive fuel pressure, delivering too much fuel to all injectors and creating a rich mixture.
- 4
Mass airflow sensor malfunction
A dirty or failing MAF sensor may under-report incoming air, causing the PCM to inject more fuel than needed for proper combustion.
How to Diagnose It
- 1
Check Faulty post-catalyst oxygen sensor — The O2 sensor downstream of the catalytic converter on Bank 2 may be failing or producing incorrect voltage signals, causing the PCM to misread exhaust oxygen levels.
- 2
Check Fuel injector stuck or leaking — A fuel injector on Bank 2 may be stuck open or leaking fuel into the combustion chamber, causing an overly rich condition that the sensor detects.
- 3
Check Failed or sticking fuel pressure regulator — A faulty fuel pressure regulator can cause excessive fuel pressure, delivering too much fuel to all injectors and creating a rich mixture.
- 4
Check Mass airflow sensor malfunction — A dirty or failing MAF sensor may under-report incoming air, causing the PCM to inject more fuel than needed for proper combustion.
How to Fix It
- 1
Replace post-catalyst oxygen sensor Bank 2
Locate and remove the oxygen sensor downstream of the catalytic converter on Bank 2, then install a new OEM or quality aftermarket sensor. Clear the code and test drive to verify.
- 2
Clean or replace fuel injectors
Have the fuel injectors professionally cleaned or replaced if stuck open. A fuel system cleaning service can often resolve sticking injectors; severe cases require replacement.
- 3
Inspect and replace fuel pressure regulator
Test fuel pressure with a fuel pressure gauge; if pressure is too high, remove and replace the fuel pressure regulator. Verify pressure returns to specification after replacement.
- 4
Clean or replace mass airflow sensor
Remove the MAF sensor and clean it carefully with MAF sensor cleaner, or replace it if damaged. A contaminated MAF sensor is a common cause of rich running conditions.
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