P0608

Electrical Diagram:

CIRCUIT DESCRIPTION

Various components apply a voltage to the Vehicle Speed Output circuit. The PCM creates the Vehicle Speed Output signal by rapidly grounding this circuit via an internal switch called a driver. The driver operates at the same rate as the VSS signal input. The various components recognize the voltage being pulled to ground as an indication of vehicle 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 0.0 volts). When the PCM commands the control circuit to a component OFF, the voltage potential of the circuit should be high (near battery voltage). If the fault detection circuit senses a voltage other than what is expected, the fault line status changes causing the DTC to set.

CONDITIONS FOR SETTING THE DTC

^ The engine speed is greater than 600 RPM.

^ The PCM detects that the commanded state of the driver and the actual state of the control circuit do not match.

^ The condition must be present for a minimum of 10 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 clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.

^ The PCM battery voltage is interrupted.

^ Use a scan tool in order to clear the MIL/DTC.

DIAGNOSTIC AIDS

This DTC will not report a pass. The scan tool status for this DTC will never report a pass, so it will appear that the diagnostic never runs.

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 Body and Accessories for further diagnosis.

3. Further circuit diagnosis may require I/P removal. The circuit from the PCM to the speedometer must be checked for being open, shorted to ground or, voltage. If you do not find any trouble, follow the appropriate I/P diagnostic procedure.

6. This DTC will not report a pass. The scan tool status for this DTC will never report a pass. The scan tool will only display when the diagnostic fails. The repair is not complete if the scan tool indicates that the diagnostic ran and failed.