What the P0654 code means
During operation, the engine speed is monitored by the PCM through several components. One of these is the Engine RPM Output Circuit, which creates a signal through a grounding process that involves a driver (an internal switch). Each driver is monitored by the PCM through a fault line, sending voltage readings to the PCM for comparison to the manufacturer's specifications. If the voltage is too high or too low compared to what it is supposed to be in the current operation conditions, the PCM will store the P0654 code.
What causes the P0654 code?
CM programming error
Faulty controller or PCM
Open or shorted circuit between the PCM and the instrument panel or other controllers
What are the symptoms of the P0654 code?
Symptoms may range from only a stored code and service engine soon illumination, to a no start condition, an inoperative tachometer, or even an erratic tachometer.
Common mistakes when diagnosing the P0654 code
Technicians report that the tachometer is often replaced in error when the PCM driver is at fault.
What repairs can fix the P0654 code?
1. Repair any defects in the system circuitry, replacing loose, corroded, or broken electrical components as necessary.
2. Replace a faulty instrument cluster.
3. Repair an open or shorted instrument cluster harness.
4. Replace a faulty tachometer.
5. Replace a bad crankshaft or camshaft sensor.
6. Replace a faulty PCM, in rare cases.