Vehicle speed signal is implausible.
SYMPTOMS
- Check-engine light
- Rough idle or hesitation
- Reduced performance
- Worse fuel economy
LIKELY CAUSES
- Faulty or drifting vehicle speed sensor
- Wiring/connector fault
- Mechanical/intake condition skewing the reading
- ECM/PCM fault (rare)
DIAGNOSIS STEPS
- Compare vehicle speed sensor live data against other sensors for plausibility
- Inspect wiring and connector
- Check for related mechanical causes (leaks, restriction)
- Verify reference voltage and ground
- Replace the sensor if out of spec
RELATED PARTS
- Vehicle speed sensor