P0654

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION
The PCM supplies a voltage to the Engine Speed Output circuit. The PCM creates the Engine Speed Output signal by rapidly grounding this circuit via an internal switch called a driver. The other components on this circuit recognize the voltage being pulled to ground as an indication of engine speed.

The driver supplies the ground for the component being controlled. Each driver has a fault line which the PCM monitors. When the PCM commands a component ON, the voltage of the control circuit should be low (near 0 volts). When the PCM commands the control circuit to a component OFF, the voltage potential of the circuit should be high (near battery voltage). It the fault detection circuit senses a voltage other than what is expected, the fault line status changes causing the DTC to set.

CONDITIONS FOR RUNNING THE DTC
- The engine speed is greater than 600 RPM.
- The ignition voltage is between 6.0 volts and 16.0 volts.

CONDITIONS FOR SETTING THE DTC
- The PCM detects that the commanded state of the driver and the actual state of the control circuit do not match.
- All conditions present for a minimum of 10.0 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The PCM stores the DTC information into memory when the diagnostic runs and fails.
- The Malfunction Indicator Lamp (MIL) will not illuminate.
- The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
- A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
- A last test failed (Current DTC) will clear when the diagnostic runs and does not fail.
- The PCM battery voltage is interrupted.
- Use a scan tool in order to clear the MIL/DTC.

DIAGNOSTIC AIDS
Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid determining how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed. For an intermittent, refer to Symptoms. Testing and Inspection

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.

IMPORTANT: If the I/P is completely inoperative, refer to Electrical Diagnosis for further diagnosis.
3. Further circuit diagnosis may require I/P removal. Check the circuit from the PCM to the tachometer for being open, shorted to ground or, voltage. If you can not find any trouble, follow the appropriate I/P diagnostic procedure.
6. The repair is not complete if the scan tool indicates that the diagnostic ran and failed.