P218AThrottle Actuator B Control System - Idle Position Not Learned
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P218A is the throttle B counterpart of P2176: on engines with a second electronic throttle, usually one per cylinder bank, that second unit failed to learn its closed rest position. GM's 2023 table 23OBDG07 runs the same three-step learn for bank 2 as for bank 1. First the plate must reach the closed target within 1.5 %, then the motor has to press it onto the stop with enough duty cycle, and finally the stored voltages must fall inside 0.33-0.58 V for sensor 1 and 4.42-4.67 V for sensor 2; any failed step stores the code within one trip. No other manufacturer documents P218A publicly. Ice, carbon, a weak motor or wiring faults at throttle B are typical causes, and engine power may be limited. Electrical motor faults of throttle B use P210A.
- What you may notice
- Check engine lamp
- Uneven idle between the banks
- Reduced power
- Likely causes
- LikelyCarbon or ice keeping throttle B off its closed stop
- PossibleWeak motor or gear wear in throttle unit B
- PossiblePosition sensors of throttle B outside the learn window
- RareSupply or signal wiring fault at throttle B
- 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 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.