P2C99Throttle Actuator A 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
- An electronic throttle relies on learned values: the closed-stop position of its sensors and, in many systems, a correction that widens the commanded opening as carbon narrows the bore. P2C99 says a learned value for throttle A has run into its permitted limit, so the module can no longer compensate. No manufacturer publishes P2C99. GM shows both ideas elsewhere: its 2023 tables (23OBDG07) fail the lower-stop learn of throttle sensor bank 1 with in-house codes P30E3/P30E4 within one trip, and GM patents cap the learned throttle area correction and report how near it is to that cap as a coking value. Heavy deposits, a worn or replaced throttle body without relearn, or drifting sensors are typical. Idle may be unstable and power reduced. P2176 is the related idle-position code.
- What you may notice
- Engine warning lamp, possibly an electronic throttle warning
- Idle speed too high, too low or hunting
- Reduced power in a throttle emergency mode
- Likely causes
- LikelyHeavy carbon deposits in the throttle bore needing more correction than allowed
- PossibleThrottle body cleaned or replaced without resetting and relearning the adaptation
- PossibleWorn throttle shaft, plate or end stop shifting the closed position
- RareThrottle position sensor 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 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.