P0654Engine RPM Output Circuit/Open
- Generic OBD-II code · Powertrain
- How the car detects it
- The engine module switches this hard-wired output with its own driver and checks the circuit electrically (open, short to ground or voltage) – it cannot see whether the lamp lights; on CAN-based cars such faults appear as U codes. P0654 concerns the engine speed output: the module turns the crankshaft signal into a cleaned-up square wave for the tachometer and other modules – Saab's 1999 9-3, for example, sends two pulses per revolution, about 30 Hz at idle. P0654 reports an open circuit or other fault on this output. Saab's EDC16 diesels use P0654 differently (a sensor supply group). No manufacturer document available to us uses this code; the description follows CARB and the component. The tachometer then reads zero or jumps; devices using the signal may fail, while the engine itself runs normally because the crankshaft input is intact.
- What you may notice
- Tachometer reads zero or jumps
- Functions using the speed signal disturbed (accessories, cruise control, shift indicator)
- Check engine light depending on the maker
- Likely causes
- LikelyWire between module and tachometer or receiver open, connector corroded
- PossibleOutput wire shorted
- PossibleInstrument cluster or receiving module faulty (input stage)
- RareOutput driver in the module faulty
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.