P0601

Circuit Description
The Powertrain Control Module (PCM) is the control center of the fuel injection system. It constantly looks at the information from various sensors, and controls the systems that affect vehicle performance. The PCM also performs the diagnostic function of the system. It can recognize operational problems, alert the driver through the Malfunction Indicator Lamp (MIL) (Check Engine), and store a DTC or DTCs which identify the problem areas to aid the technician in making repairs. An Electrically Erasable Programmable Read Only Memory (EEPROM) is used to house the program information and the calibrations required for engine, transmission, and powertrain diagnostics operation. The PCM uses a value called a Checksum for error detection of the software. The Checksum is a value that is equal to all the numbers in the software added together. The PCM adds all the values in the software and if that value does not equal the Checksum value, a Checksum error is indicated.

Conditions for Setting the DTC
The PCM detects more than 3 incorrect checksums.

Action Taken When the DTC Sets
- The MIL will illuminate.
- The PCM will attempt to record operating conditions at the time this failure is detected, however since this is a internal PCM failure, this information may or may not be reliable. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- The MIL will turn "OFF" after three consecutive ignition cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm up cycles without a fault.
- DTCs can be cleared by using a scan tool.

DTC P0601 - PCM Memory:

Test Description
Numbers below refer to the step numbers on the Diagnostic Table.
1. The OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored on the scan tool for later reference.
2. Replacement PCM must be reprogrammed. Refer to the latest Techline information for programming procedures.