P2C9AThrottle Actuator B Control Exceeded Learning Limit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- Throttle B exists only on engines with two electronically driven throttle bodies, usually one per cylinder bank on large V engines. P2C9A means a learned value of that second throttle – its closed-stop reference or the airflow correction stored for it – has reached the edge of the allowed range. Since both throttles must deliver matching air, a large learned offset on one side alone hints at deposits, a sticking plate or a replaced unit on that side. No manufacturer documents P2C9A. GM's 2023 tables handle the bank 2 throttle sensor with separate in-house codes (P30E5/P30E6) for the same stop-learn limit, judged within one trip. Expect rough or uneven idle, limited power if the module restricts the throttle, and possibly companion codes such as P218A (idle position of throttle B not learned).
- What you may notice
- Engine warning lamp
- Uneven or hunting idle
- Reduced power if the throttle is restricted
- Likely causes
- LikelyCarbon deposits in throttle body B only
- PossibleThrottle body B replaced or cleaned without relearn
- PossibleThrottle plate B sticking or its return spring weak
- RarePosition sensor of throttle B drifting
- 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: €30 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.