The P0638 trouble code indicates that the Engine Control Module (ECM) has detected a range or performance issue with the throttle actuator control circuit for bank 1. This code is set when the ECM determines that the actual position of the throttle actuator deviates from the expected position range.
P0638 Throttle Actuator Control Range/Performance (Bank 1)
Code symptoms P0638.
1. Check Engine Light (CEL) is illuminated on the dashboard.
2. Reduced engine power or acceleration.
3. Engine may hesitate or stumble during acceleration.
4. Rough idling or stalling.
5. Vehicle may go into limp mode.
This code is common in brands such as:: Chevrolet, Renault, Ford, Toyota, Nissan, Mercedes Benz, Honda.
Causes of the code P0638.
1. Faulty throttle actuator or throttle position sensor.
2. Damaged wiring or connectors in the throttle actuator control circuit.
3. Carbon buildup in the throttle body.
4. Vacuum leaks in the intake system.
5. ECM or PCM malfunction.
Code Solutions P0638.
1. Inspect the throttle actuator and throttle position sensor for any signs of damage or wear. Replace any faulty components as needed.
2. Check the wiring harness and connectors in the throttle actuator control circuit for corrosion, damage, or loose connections. Repair or replace any damaged wiring or connectors.
3. Clean the throttle body to remove any carbon buildup that may be affecting its operation.
4. Perform a smoke test to check for vacuum leaks in the intake system. Repair any leaks found.
5. Use a diagnostic scan tool to monitor the throttle position sensor’s data and perform a throttle relearn procedure if necessary.
6. Clear the trouble codes and perform a test drive to verify that the issue has been resolved. If the code persists, further diagnosis may be required.