P2099 — Post Catalyst Fuel Trim System Too Rich (Bank 2)
Low severityWhat it means
P2099 is stored when the engine control unit sees a fault involving the post-catalyst fuel trim on bank 2. On many engines the control unit also trims fuel based on the downstream oxygen sensor; this code means that post-catalyst correction on bank 2 hit its limit. “Rich” means the exhaust shows too much fuel (or too little air), and the control unit has run out of room to remove fuel to correct it.
Common symptoms
- Black smoke, a fuel smell or poor economy
- Often only a check engine light
- Slightly higher fuel use
- Failed emissions test
Likely causes
- A leaking injector or high fuel pressure
- A faulty oxygen sensor or a restricted air intake
- A worn downstream oxygen sensor
- An exhaust leak or an aging catalytic converter
What to check first
- Check fuel pressure and the injectors for leaks
- Watch fuel trims and oxygen-sensor data in live data
- Compare upstream and downstream oxygen-sensor signals on bank 2
- Inspect the exhaust for leaks
Can you keep driving?
Generally drivable; repair to keep fuelling efficient and to pass emissions.
Frequently asked questions
What is the most common cause of P2099?
The most likely cause is: A leaking injector or high fuel pressure. Several other faults can set P2099 as well, so confirm the real cause with live data and the checks above before replacing any parts.
Can I just clear P2099 and keep driving?
Clearing P2099 with an OBD2 scanner turns the warning light off, but if the underlying fault has not been repaired the code will usually come back within a few drive cycles. Fix the cause first, then clear the code to confirm the repair worked.
How serious is P2099?
P2099 is a low-severity code. It rarely affects how the car drives, but it is still worth fixing so the engine runs efficiently and passes an emissions test.
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