Closed Loop Fueling Not Achieved -- Bank 2 (Volkswagen/Audi)
What does P1129 mean?
The P1129 code means the vehicle's onboard diagnostic system has detected: Closed Loop Fueling Not Achieved -- Bank 2 (Volkswagen/Audi). This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Poor fuel economy
- Rough idle
- Engine stumble or hesitation
- Failed emissions test
Probable Causes (Ranked by Likelihood)
- Vacuum leak in intake system Very High
- Faulty oxygen sensor (bank 2) High
- Dirty or clogged fuel injectors on bank 2 Moderate
- Exhaust leak before the oxygen sensor on bank 2 Moderate
- Failing fuel pressure regulator Low
Step-by-Step Diagnostic Procedure
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Check for vacuum leaks using a smoke machine -- focus on bank 2 intake
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Monitor fuel trim data for bank 2 with a scan tool
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Test the front oxygen sensor on bank 2 for proper response
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Inspect for exhaust leaks before the bank 2 catalytic converter
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Check fuel pressure and fuel injector balance test
Frequently Asked Questions
Can I drive with code P1129?
You can drive short distances. Like P1128, the engine is not achieving proper fuel control on bank 2. This can lead to catalytic converter damage if not addressed.
What is the difference between P1128 and P1129?
P1128 refers to bank 1 (the side with cylinder 1), while P1129 refers to bank 2 (the opposite side). If both codes are present, a common cause like a vacuum leak or fuel pressure issue is likely.
Is P1129 expensive to fix?
Typical repairs cost $100 to $600. Vacuum leak repairs are on the lower end, while oxygen sensor or fuel injector replacement is on the higher end.