Throttle Actuator Control Range/Performance (Bank 1)
The P0638 code indicates that the Powertrain Control Module (PCM) has detected a malfunction in the throttle actuator control system, specifically that the actual throttle position does not match the commanded position within a specified range or performance parameter. This can be caused by a faulty throttle actuator motor, a sticking throttle plate, wiring issues, or a malfunctioning throttle position sensor. The system is designed to ensure precise control of the throttle plate for optimal engine performance and emissions.
1. Most Common Causes
- Carbon or dirt buildup on the throttle body restricting throttle plate movement
- Faulty or damaged throttle actuator motor (inside the throttle body)
- Damaged or out-of-calibration throttle position sensor (TPS)
- Wiring harness issues in the throttle body circuit (short, open, or high resistance)
- Corroded or loose electrical connections at the throttle body or PCM connector
- Internal PCM failure in the actuator driver circuit (uncommon)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine power or limp mode
- Poor acceleration or hesitation
- Rough idle or stalling
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for additional codes.
Step 2: Visually inspect the throttle body for carbon buildup or sticking.
Step 3: Test the throttle actuator motor and throttle position sensor with a multimeter.
Step 4: Check wiring and connectors for damage, corrosion, or loose connections.
Step 5: Perform a throttle body relearn procedure if repairs are made.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code as it can cause reduced engine power, poor acceleration, and potential stalling, which may lead to unsafe driving conditions.
How much does it cost to fix?▼
The cost to fix P0638 typically ranges from $50 to $150 for diagnostic and cleaning, but could be higher if replacement of the throttle body or actuator is needed.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.