P0638Throttle Actuator Control Range/Performance Bank 1
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- The electronic throttle motor positions the throttle plate; P0638 means the actuator does not follow its command on bank 1 (or the only throttle): target and actual angle from the two position sensors differ, or the motor needs too much duty cycle to hold the position. Subaru (also sold as Saab 9-2X) sets it at more than 3.5° deviation for 250 ms or over 95 % duty cycle for 2 s, lights the lamp at once and lets the spring set the plate to about 6° – raised idle, almost no power. GM's Saab 9-4X V6 uses more than 80 % duty cycle for over 1 s, lamp in the first trip. Mazda's CX-9 set it after frosty nights when condensation froze the throttle and fixed it with software that moves the plate after switch-off. Ford reports the same function as P2111/P2112.
- What you may notice
- Check engine or electronic throttle light
- Limp mode: much reduced power, raised idle
- Delayed or jerky throttle response
- Often after a cold start in frost
- Likely causes
- LikelyThrottle dirty, sooted or stiff
- PossibleIcing from condensation in frost
- PossibleThrottle motor or gears worn
- PossibleResistance in the motor control wires
- RareModule or software
- 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: €50 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.