Cause
Throttle plate stuck open
The throttle plate held open when it should close, so the engine takes in more air than commanded. It is the safety-relevant direction of a stuck throttle and the module treats it accordingly — a plate that will not return means airflow the driver did not request, so a reduced-power mode follows immediately.
Idle is where it shows. The module commands the plate closed for idle, sees the plate report a larger opening, and cannot bring engine speed down — so the complaint is a high idle that will not settle, together with a throttle actuator or airflow code. A high idle that persists with the pedal untouched is the signature.
Carbon and mechanical obstruction are the causes, in that order. Deposits build around the plate's edge exactly where it seats at idle, and a foreign object, a broken return spring or a distorted plate account for the rest. Check the plate closes fully and freely by hand with the throttle body off — this must never be diagnosed by driving the vehicle, because an uncommanded opening is a genuine hazard.
Typically a moderate job.
Some of these codes mean you should stop driving
3 of the 4 codes this can cause indicate a fault where continuing to drive risks damage or is unsafe. Which one you have matters more than the cause does — read the code's own page before deciding.
Codes this can cause (4)
Codes where this is a likely explanation first, rather than merely a possible one.
- P2111 Throttle Actuator A Control System — Stuck Open Likely for this code Stop driving Critical
- P2105 Throttle Actuator Control System — Forced Engine Shutdown Stop driving Critical
- P2172 Throttle Actuator Control System — Sudden High Air Flow Detected High
- P0219 Engine Overspeed Condition Stop driving Critical
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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