A P0638 OBDII code indicates an issue with the throttle actuator control system, specifically “Throttle Actuator Control Range/Performance Bank 1.” This article documents a real-world experience of diagnosing and resolving this error code in a Volkswagen vehicle.
The initial symptoms included the car entering limp mode. A standard OBD-II reader revealed low throttle values despite a responsive accelerator pedal. Visual inspection and cleaning of the throttle body didn’t resolve the issue. Live data from the OBD-II scanner confirmed the throttle wasn’t opening correctly.
The vehicle was driven to a local garage in limp mode without further incident. The garage diagnosed the problem as a faulty throttle body and quoted a price of £780 for a replacement from Volkswagen and installation.
To reduce costs, a new Magneti Marelli throttle body (04C133062D) was sourced online for £235. After a five-day wait, the part arrived and was taken to the repair shop for installation. The shop charged £95 + VAT for one hour of labor and calibration.
Post-repair, the car’s performance returned to normal. The unexpected failure of the throttle body on a relatively new car with low mileage (4 years old, 30k+ miles) was noted. The total cost of the repair, including the part and labor, was significantly less than the initial quote from the garage using the VW part. This underscores the potential for cost savings when sourcing parts independently. While online resources can provide valuable diagnostic information, professional expertise is often crucial for accurate diagnosis and repair.
