Throttle Actuator Control Range/Performance (Bank 2)
Code P0639 indicates that the Powertrain Control Module (PCM) has detected a malfunction in the throttle actuator control system for Bank 2 (the side of the engine opposite cylinder #1). This typically means the throttle actuator is not responding correctly to commands, or its range of motion is outside expected parameters. The system uses an electronic throttle control motor to open and close the throttle plate based on accelerator pedal input. A fault can cause reduced engine power, poor acceleration, or limp mode.
1. Most Common Causes
- Throttle body dirty, sticking, or carbon deposits preventing free butterfly movement
- Internal failure of the throttle actuator motor (open or short circuit)
- Defective throttle position sensors (TPS) with erratic or noisy signal
- Damaged, corroded, or shorted wiring/connectors in the actuator or TPS circuit
- Internal PCM failure (actuator drivers or signal processing)
- Low battery voltage or charging system issues affecting actuator power supply
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 code P0639 and check for related codes.
Step 2: Visually inspect throttle actuator wiring and connectors for damage or corrosion.
Step 3: Test throttle actuator motor resistance and voltage supply using a multimeter.
Step 4: Clean throttle body and plate if carbon buildup is present.
Step 5: If all else fails, replace the throttle actuator assembly and reprogram if necessary.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. The vehicle may enter limp mode, limiting speed and acceleration, which can be dangerous in traffic.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Repair costs vary: cleaning throttle body ($50-$100), replacing throttle actuator ($200-$500), or PCM replacement ($500-$1000).
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.