Post Catalyst Fuel Trim System Too Rich (Bank 2)
The P2099 code means the vehicle's onboard diagnostic system has detected: Post Catalyst Fuel Trim System Too Rich (Bank 2). This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- moderate
- Estimated cost
- $100 - $800 (parts and labor)
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Common Symptoms
- Check Engine Light on
- Engine runs rich on Bank 2
- Black exhaust smoke possible
- Fuel smell from exhaust
- Reduced fuel economy
Probable Causes (Ranked by Likelihood)
- Failed rear oxygen sensor on Bank 2 reading lean falsely Very High
- Internal catalytic converter failure on Bank 2 High
- Fuel injector leaking on Bank 2 Moderate
- Coolant leak into Bank 2 combustion chamber Low
Common Fixes by Vehicle
What techs usually find when diagnosing P2099 on specific vehicles — tap your vehicle for the fix and the exact part:
2005-2010 Ford F-150/Expedition 5.4L 3V easy DIY
Ford P2099 = Post Catalyst Fuel Trim bank 2 TOO RICH. Usually indicates a failed downstream O2 sensor or a partially failed catalytic converter. Replace the bank 2 downstream O2 first (Motorcraft). If P2099 returns, the cat is likely saturated -- check for P0430 alongside. Confirm the exact part for your year and engine with a retailer's fitment lookup or your VIN before ordering - these applications split by engine and build date.
Labor: 45 min2005-2012 Cadillac CTS/STS 3.6L easy DIY
Cadillac CTS P2099 = post-cat fuel trim rich bank 2. Most commonly a failed bank 2 downstream O2. The sensor reading rich causes the PCM to subtract fuel that doesn't need to be subtracted, throwing the trim out of range. Replace with an OE-quality AC Delco unit or equivalent OE. Confirm the exact part for your year and engine with a retailer's fitment lookup or your VIN before ordering - these applications split by engine and build date.
Labor: 45 min2007-2013 Chevy Silverado/Tahoe 5.3L/6.2L easy DIY
GM 5.3L/6.2L P2099 on bank 2 -- replace the downstream O2 sensor with AC Delco. If the catalytic converter is aftermarket, it may not meet OBD-II efficiency requirements and will trigger post-cat trim codes regardless of sensor. CARB-compliant cats are required on these.
Labor: 45 minFrequently Asked Questions
What does P2099 mean?
P2099 indicates the ECM has detected that the post-catalyst fuel trim on Bank 2 is too rich, meaning the system cannot properly adjust fuel delivery based on rear O2 sensor feedback.
Can a bad catalytic converter cause this?
Yes, a failing or internally damaged catalytic converter can cause abnormal rear O2 sensor readings, which triggers post-catalyst fuel trim codes.
Should I replace the oxygen sensor first?
Check for exhaust leaks first, as they are a common and inexpensive cause. Then test the O2 sensor data. Only replace the sensor if testing confirms it is faulty.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Monitor Bank 2 rear O2 sensor switching rate and voltage
-
Check Bank 2 fuel injector balance
-
Inspect Bank 2 catalytic converter for internal failure
-
Check for coolant loss without visible leaks
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
- Cross-checked against the SAE J2012:2002 DTC table (2026-08-27)archived scan of the SAE standard — readable copy, not SAE’s current edition
Commonly Affected Vehicles
- 2010-2020 Toyota Tundra 5.7L
- 2008-2018 Ford F-150 5.0L
- 2010-2019 Chevrolet Silverado 5.3L
- 2009-2019 Ram 1500 5.7L
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