P2D1BExhaust Flow Control Valve C Position Not Learned
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P2D1B closes the valve C series: the control unit holds no valid end stop values for the third exhaust flap, so it cannot translate its position feedback into a reliable angle. No manufacturer documents P2D1B publicly, and so far even the A and B versions P2D11 and P2D12 are rare in published material. GM's 23OBDG07 tables show the principle for two exhaust valves: during an end stop learn phase the feedback is watched for a valve stuck at a stop, and a separate test flags end stops that were never learned after 4 seconds, with the MIL on the second trip. GM bulletin PIC6289C ties such faults to new cars and recent exhaust work and prescribes a scan tool relearn instead of new parts. Ford's 25-2144 likewise needs an alignment after fitting a new actuator.
- What you may notice
- Check engine light shortly after exhaust or battery work
- Flap C hunting, buzzing or rattling
- Sound modes do not switch as expected
- Likely causes
- LikelyLearn run for flap C not completed after installation or repair
- PossibleLearned end stops lost after battery disconnection
- PossibleFlap blocked or binding so the learn run aborts
- RareEngine software that needs an update before the learn succeeds
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €0 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.