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 and the engine is running. |
| • | Crank sensor signals recieved |
Conditions for Setting the DTC
| • | No crank sensor DTC(s) set. |
| • | An improper voltage has been detected on the tachometer output control circuit. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the MIL during the second consecutive trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed. |
| • | The history DTC will clear after 40 consecutive warm-up cycles have occured without a malfunction. |
| • | The DTC can be cleared by using the scan tool Clear Info function or by disconnection teh PCM battery feed. |
Diagnostic Aids
Refer to Instrument Cluster System Check in Instrument Panel, Gauges, and Console for additional diagnostic information.
Check for the following conditions:
| • | Poor connection at the PCM or instrument cluster. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. |
| • | 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 tachometer control circuit at the PCM harness connector while moving connectors and wiring harnesses related to the tachometer control circuit. A change in voltage will indicate the location of the fault. |
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On Board Diagnostic (OBD) System Check performed | -- | ||||||
2 | Select DTC Info, Last Test Fail and observe DTC(s). Is DTC P0654 set? | -- | ||||||
3 |
Does the scan tool indicate DTC P0654 failed this ignition? | -- | Go to Diagnostic Aids | |||||
4 |
Does the tachometer operate properly. | -- | Go to Powertrain Control Module Controlled Tachometer Diagnosis | |||||
5 | Was the Diagnostic System Check in ABS/TCS performed? | -- | Go to ABS/TCS System Check | |||||
6 | If a condition is found that requires repairs, repair as necessary. Is the action complete? | -- | System OK | -- |
