Circuit Description
The control module 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 control module adds the data in all of these memory locations. This value is called the checksum. The control module also performs the same function when the ignition is turned ON. If at key ON the checksums do not match, this diagnostic trouble code (DTC) will be set.
Because 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 control module illuminates the malfunction indicator lamp (MIL) the first time the diagnostic runs and fails. |
| • | The control module will set the DTC and records the operating conditions at the time the diagnostic fails. The control module stores the failure information in the scan tools Freeze Frame/Failure Records. |
Conditions for Clearing the MIL or DTC
| • | The control module 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. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle. |
| • | Use a scan tool in order to clear the DTCs. |
Diagnostic Aids
If the battery has been disconnected for any reason it could cause DTC P0603 to 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.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
2 |
Did this DTC reset? | -- | System OK | |
3 |
Important: The replacement VCM must be programmed. Replace the VCM. Refer to VCM Replacement/Programming . Is the action complete? | -- | -- | |
4 |
Does the scan tool indicate that the diagnostic Passed? | -- | ||
5 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to applicable DTC | System OK |
