P0604

DTC P0604 VCM Random Access Memory (RAM)

Circuit Description
The VCM contains memory in which incoming data can be temporarily stored. This is called Random Access Memory (RAM). Ram is cleared and tested when the ignition is turned ON. If the data read from the memory locations does not match the data that was just stored to those locations during this testing, a DTC P0604 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 between the data read from a memory location and the data written to that location.

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.

Step 1:

Steps 2 - 4:

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. Replace the VCM even if this DTC exists only in history.