P0638
Throttle Actuator Control Range or Performance Bank 1
The drive-by-wire throttle actuator on bank 1 does not respond as commanded - actuator slow, gearing slipping, or position feedback offset against actual blade angle.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Symptoms
- Check engine light on
- Reduced throttle response, possible limp mode
- Hesitation or surging
- Idle too high or too low
Common causes
Ordered by how often each turns out to be the cause.
- Actuator sticking due to carbonCommon
Parts involved
- Throttle Actuator B1
- Throttle Position Sensor B1
P0638 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.