Circuit Description
The PCM uses an electrically erasable programmable read-only memory (EEPROM) in order to store the software and calibration information. The PCM uses a checksum in order to verify the integrity of the information. At the time of programming, the PCM calculates a checksum and stores the value in the EEPROM. At key ON, the PCM retrieves the information and performs a checksum. The PCM compares the key ON value to the value stored in the EEPROM. If the checksum at key ON does not match the stored checksum, this diagnostic trouble code (DTC) will set.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
The PCM detects a calculated checksum value that does not match the stored checksum value.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
DTC P0601 indicates that the contents of the EEPROM have changed since the PCM was programmed. The PCM must be replaced. Remember to program the replacement PCM with the correct software and calibration for the vehicle.
If the condition is intermittent, refer to Intermittent Conditions .
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | |
Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- |
