Symptoms of P0546
- 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 P0546
- 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
- Review EGT signal voltage, reference or bias voltage, ground path, engine load, boost, fueling, regeneration status where equipped, and freeze-frame data.
- Inspect for open grounds, short-to-voltage faults, connector heat damage, sensor wiring near exhaust, and true excessive exhaust temperature conditions.
- Compare cold and hot readings to determine whether the signal is stuck high or reacting to actual overheating.
Related OBD-II codes
These nearby speed / idle entries can help compare wording and pin down the fault area.