Throttle Actuator Control Throttle Body Range/Performance

Possible causes

• CommonCarbon build-up making the throttle plate stiff
• CommonFailed throttle actuator motor
• CommonCorroded or damaged connector at the throttle body
• CommonWiring damage between the module and the throttle body
• CommonThrottle body never relearned after cleaning or replacement
• RareFailed control module driver

What you might notice

• Sudden loss of power - reduced-power mode
• Engine will not rev beyond a low limit
• Rough or unstable idle
• Warning light for reduced engine power
• Engine may not start

What to check, in order

1. Remove and inspect the throttle body for carbon around the plate and its bore.
2. Check the plate returns fully to its rest position when the motor is unpowered - the return spring holds it at a small default opening, and carbon can stop it reaching that.
3. Be aware that power can be cut without warning. Avoid overtaking and motorway slip roads until this is fixed.
4. Inspect the throttle body for carbon. On a drive-by-wire throttle, cleaning without running the relearn procedure afterwards can leave the idle worse than before - check whether a relearn is specified before starting.
5. Compare commanded against actual throttle position on the live data screen through a full sweep.
6. Inspect the connector at the throttle body for corrosion.
7. Measure the actuator motor resistance against specification.