P0654

Circuit Description
The PCM supplies the ground to energize the Instrument Cluster tachometer. When the ignition switch is first turned on the PCM grounds the tachometer circuit The circuit will remain grounded until the PCM receives the first 24X reference pulse. Once the 24X reference pulse is received, the PCM controls the pulse frequency in relationship to engine RPM. The tachometer is controlled at a rate of two pulses per crankshaft revolution.

Conditions for Running the DTC
The ignition is on.

Conditions for Setting the DTC
^ An improper voltage level has been detected on the Tachometer Output Control circuit.
^ The above condition present for at least 30 seconds.

Diagnostic Aids
Check for the following conditions:
^ Poor connection at the PCM. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Refer to Intermittents and Poor Connections Diagnosis.
^ Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, disconnect the PCM, turn the ignition on and observe voltmeter connected to the MIL circuit at the PCM harness connector while moving connectors and wiring harnesses related to the MIL control circuit. A change in voltage will indicate the location of the fault. Refer to Intermittents and Poor Connections. Refer to Wiring Repairs in Diagrams. Symptom Related Diagnostic Procedures

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Test Description
The numbers below refer to the step numbers on the diagnostic table:
3. Normally, ignition feed voltage should be present on the output driver circuit with the PCM disconnected and the ignition turned ON.
4. Checks for a shorted component or a short to battery positive voltage ON the output driver circuit. Either condition would result in a measured current of over 0.5 amps.
5. Checks for a faulty instrument cluster.
14. A fault in the 24X Crankshaft/Camshaft position sensors feed or ground circuits will result in the loss of both PCM input pulses. Without a 24X reference pulse the PCM can not begin tachometer pulse control causing an inoperative tachometer.
18. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed. Refer to PCM Replacement and Programming Procedures in Powertrain Control Module (PCM) and Sensors.