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.
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 control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles. |
| • | The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool 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, 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 could 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 in Wiring Systems.
If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Important: Before clearing the DTCs, use the scan tool Capture Info to save the Freeze Frame and Failure Records for reference. The control module's data is deleted once the Clear Info function is used. Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | |
2 |
Did this DTC reset? | -- | Go to Step 3 | System OK |
3 |
Is the action complete? | -- | Go to Step 4 | -- |
4 |
Does the scan tool indicate the diagnostic Passed? | -- | Go to Step 5 | |
5 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to the applicable DTC table | System OK |
