Damaged, chafed or broken wiring in the RPM output circuit between the engine control unit and the instrument cluster; Corroded, loose or pushed-out pins at the engine control unit or instrument cluster connector; Faulty instrument cluster or its internal tachometer driver circuit; Fault in a module that shares the RPM signal, such as a transmission or body control module, or on a data network where the signal is sent digitally; Internal fault in the engine control unit output driver; Poor power or earth supply to the engine control unit or cluster.

P0654

Engine RPM Output Circuit/Open.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
6: AreaComputer and output circuits
54: FaultThe specific fault in that area

What it means

P0654 is a generic code meaning the engine control unit has detected a fault in the engine speed (RPM) output circuit, which feeds the rev counter on the instrument cluster. The control unit monitors the signal it sends and sets the code when it sees an open circuit or a signal that does not match what it is commanding. It is usually a wiring, connector or cluster issue rather than an engine fault, but the exact signal path varies by model.

Symptoms

Rev counter (tachometer) not working, flickering or reading incorrectly
Malfunction indicator lamp on
Rev counter needle dropping to zero while the engine runs normally
Possible intermittent stalling or rough running on some models if the signal is shared with other systems
Other cluster warning lights or gauges behaving oddly

Possible causes

Damaged, chafed or broken wiring in the RPM output circuit between the engine control unit and the instrument clusterlikely
Corroded, loose or pushed-out pins at the engine control unit or instrument cluster connectorlikely
Faulty instrument cluster or its internal tachometer driver circuitpossible
Fault in a module that shares the RPM signal, such as a transmission or body control module, or on a data network where the signal is sent digitallypossible
Internal fault in the engine control unit output driverrare
Poor power or earth supply to the engine control unit or clusterpossible

How to diagnose

Read all stored codes and freeze frame data, and note whether other modules have related or network communication codes
Check whether the rev counter works, and compare it with engine speed shown in live data on a scan tool
Visually inspect the wiring harness between the engine control unit and instrument cluster for chafing, heat damage and rodent or water damage
Inspect the connectors at the engine control unit and cluster for corrosion, bent or loose pins and moisture
Check battery condition and the power and earth supplies to the engine control unit and cluster against the manufacturer wiring diagram
Test the RPM signal circuit for continuity, short to earth and short to voltage with the connectors disconnected, following the model-specific procedure
Check the signal at the cluster with an oscilloscope or suitable meter while the engine runs, noting that the signal type depends on the model
Clear the code and road test to see whether it returns

How to fix

Repair or replace damaged wiring in the RPM output circuit
Clean, repair or replace corroded or damaged connectors and terminals
Repair power or earth supply faults found at the control unit or cluster
Repair or replace the instrument cluster if the tachometer driver is faulty, with coding or programming as the manufacturer requires
Repair or replace the engine control unit only after wiring, supplies and the cluster are proven good
Apply an updated manufacturer calibration only if a known software fault is documented for that vehicle

Can I keep driving?

Low severity

The car can normally be driven while you book it in, as the fault usually affects only the rev counter. If it is stalling, running badly or other warnings appear, have it checked sooner.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.