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.
Medium severity. Can I keep driving?If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
Symptoms
- Tachometer reads zero or jumps
- Functions using the speed signal disturbed (accessories, cruise control, shift indicator)
- Check engine light depending on the maker
Most likely causes
- Wire between module and tachometer or receiver open, connector corroded
- Output wire shorted
- Instrument cluster or receiving module faulty (input stage)
- Output driver in the module faulty
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
What each character of P0654 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 6: Control modules and outputs
- 54: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0654?
If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
What causes code P0654?
The most common causes are: wire between module and tachometer or receiver open, connector corroded; output wire shorted; instrument cluster or receiving module faulty (input stage).
Related codes
- P0335Crankshaft Position Sensor A Circuit
- P0322Ignition/Distributor Engine Speed Input Circuit No Signal
- P0655Engine Hot Lamp Output Control Circuit
- P0656Fuel Level Output Circuit
- U0155Lost Communication with Instrument Panel Cluster
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.