Symptoms of P0557
- Unstable, high, or low idle, or stalling.
- Erratic speedometer, cruise-control, or shift behaviour.
- Check-engine light with a hesitation or surge.
Common causes of P0557
- A dirty throttle body, idle-control valve, or throttle-position sensor.
- A failing vehicle-speed or wheel-speed sensor, or its wiring.
- Vacuum leaks or a related sensor forcing the idle/speed strategy.
Useful checks before replacing parts
- Check sensor signal voltage, reference voltage, ground, booster pressure data, brake pedal status, freeze-frame data, and related low-input codes.
- Inspect for short-to-ground faults, open reference circuits, connector corrosion, vacuum hose faults, low booster vacuum, and sensor internal failure.
- Compare the electrical signal with actual booster vacuum or pressure using service information and appropriate test equipment.
Related OBD-II codes
These nearby speed / idle entries can help compare wording and pin down the fault area.