OBD-II · Engine and powertrain (P)
P0638
Throttle actuator control range/performance bank 1
What it means
The electronic throttle does not follow the ECU's commands closely enough on bank 1.
Symptoms
- reduced power or limp mode (EPC light on VW group cars)
- poor or no response to the accelerator
- raised or unstable idle
- engine warning light
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | dirty or sticking throttle body |
| 02 | worn throttle motor or gears |
| 03 | motor wiring or connector fault |
| 04 | low battery voltage |
| 05 | throttle adaptation needed |
What to check, step by step
- 01Check the battery and charging voltage
- 02Inspect the throttle body for carbon, oil or ice that stops the plate moving, and clean it with the ignition off
- 03Check the motor connector and wiring for corrosion and loose pins
- 04Run the throttle adaptation (basic settings) with a scan tool and watch actual versus commanded position
- 05Replace the throttle body if the motor or gears are worn