P2099 Post-catalyst fuel trim system too rich (bank 2)
What P2099 means
The rear oxygen sensor after the catalytic converter fine-tunes the mixture on each bank. P2099 means this fine-tuning has reached its rich limit on bank 2 (the side without cylinder 1): the rear sensor sees too little oxygen. The engine is likely delivering too much fuel on that bank.
P2099 is a generic SAE J2012 code: it means the same on every make. The exact cause still depends on the car, so read the freeze-frame data before replacing parts.
At a glance
- Severity
- High
- Typical repair cost
- 60–1500 €
- Workshop time
- 0.5–4 h
- Repair difficulty
- Medium
- DIY possible
- Yes
- Check engine light
- Yes
- Affects emissions test
- Yes
Parts and labour at an independent workshop in Europe. Main dealers charge more; the cause decides the bill, not the code.
Symptoms
- Check engine light on
- Higher fuel consumption
- Strong fuel or rotten-egg smell from the exhaust
- Possible rough running
Common causes
- Leaking or dripping injector on bank 2
- Fuel pressure too high from a faulty regulator
- Faulty bank 2 upstream or downstream oxygen sensor
- Faulty coolant temperature sensor causing extra fuelling
- Failing catalytic converter on bank 2
Can I keep driving with P2099?
Have it checked within a few days. Running rich wastes fuel and can overheat and damage the catalytic converter.
What to check first
- Check fuel trims on both banks and look for related codes
- Compare bank 2 front and rear oxygen sensor signals
- Check fuel pressure and look for leaking injectors
- Check the coolant temperature sensor reading against actual engine temperature
Related codes
- P2098 Post-catalyst fuel trim system too lean (bank 2)
- P2097 Post-catalyst fuel trim system too rich (bank 1)
- P2096 Post-catalyst fuel trim system too lean (bank 1)
- P20EE SCR NOx catalyst efficiency below threshold (bank 1)
- P203B Reductant (AdBlue) level sensor A circuit range/performance
- P2101 Throttle actuator control motor circuit range/performance
- P2017 Intake manifold runner position sensor/switch circuit high (bank 1)
- P2015 Intake manifold runner position sensor/switch circuit range/performance (bank 1)
Data: TORKO fault-code catalogue, built on OBDex (CC0-1.0) and reviewed against workshop practice. Informational only — it does not replace a diagnosis by a mechanic.
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