P2096Post Catalyst Fuel Trim System Too Lean (Bank 1)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- Petrol engines run a slow outer control loop on the oxygen sensor behind the catalyst that shifts the mixture target of the front sensor. P2096 means this post-catalyst trim on bank 1 has hit its limit in the lean direction. The name describes the correction, not the engine: the rear sensor keeps reporting rich exhaust, so the loop keeps taking fuel away. GM's Bosch-based 2005 V6 calls it a rich shift with a correction below -0.03 lambda; GM's 2018 four-cylinders list it as the low limit, with the integral offset at -99 % and the total offset at -50 % or less (Type B); Ford's 2020 to 2023 engines set it 5 s after reaching a rear bias trim of -0.083. Causes are therefore a skewed rear sensor or an upstream sensor reading lean. Audi found a contaminated reference air duct in the rear sensor on 4.0 TFSI engines and warns against replacing the front sensor; GM saw P2096 on new Encore and Trax 1.4 catalysts before break-in and fixed a 2017 Malibu 1.5 by software.
- What you may notice
- Malfunction indicator lamp on
- Usually no noticeable change in driveability
- Likely causes
- LikelyRear oxygen sensor skewed rich, for example a contaminated reference air duct
- PossibleFront sensor reading lean, so the engine actually runs rich
- RareCalibration issue fixed by an ECM update
- RareNew catalyst not yet broken in
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €0 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.