P0603

Steps 1 - 2:

DTC P0603 VCM Memory Reset

Circuit Description
The VCM contains a section of non volatile memory where it stores data values it needs to save when the ignition is turned OFF. This is referred to as the Keep Alive memory. After the ignition is turned OFF the VCM adds the data in all of these memory locations. This value is called the checksum. The VCM also performs the same function when the ignition is turned ON. If at key ON the checksums do not match, this DTC will be set.

Since this diagnostic pertains to an internal VCM diagnostic check, no wiring schematic is required.

Conditions for Running the DTC
The ignition switch is in the run position.

Conditions for Setting the DTC
A difference was detected in the data stored in the keep-alive memory at power-down when compared with the data retrieved from the keep-alive memory at power-up.

Action Taken When the DTC Sets
- The VCM will illuminate the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
- The VCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame and/or Failure Records.

Conditions for Clearing the MIL/DTC
- The VCM turns OFF the MIL after 3 consecutive drive trips when the test has Run and Passed.
- A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22 °C (40 °F) from the startup coolant temperature and the engine coolant temperature is more than 70 °C (158 °F) during the same ignition cycle).
- Use the scan tool Clear Information function.

Diagnostic Aids
If the battery has been disconnected the DTC P0603 may set. The VCM checks the memory at power up.

If the memory changes it will reset. An intermittent loss of power or ground to the VCM will also cause a reset.

An intermittent may be caused by any of the following conditions:
- A poor connection
- Rubbed through wire insulation
- A broken wire inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis.

If a repair is necessary, then refer to Wiring Repairs or Connector Repairs.