Central Vehicle Configuration
On some applications, the Body Control Module (BCM) transmits VIN, Tire Circumference, Axle Ratio and Cruise Control Configuration (CCC) over the vehicle CAN network to the ECM/PCM as well as to other modules in the vehicle that use this information. Valid data received by the ECM/PCM s stored into NVRAM. This feature is known as Central Vehicle Configuration.
CAN messages with this data are sent every time the vehicle is started. If the CAN messages are not received after start, a U0140 (Lost Communication with BCM) DTC is set. Next, the data is checked to ensure that it is in a valid range. If the VIN, tire, axle or CCC are not in a valid range, a U0422 (Invalid Data received from BCM) DTC is set.
The system is designed to automatically accept valid VIN, tire, axle and CCC data if only the default data ($FF) is stored. If the default VIN, tire and axle are not replaced with valid data at the vehicle assembly plant or after service, a P0630 (VIN and/or tire/axle not programmed) DTC is set and the MIL is illuminated.
Once the PCM has valid VIN, tire, axle and CCC data, and new data is received which does not match the currently stored data, the new data is not stored into NVRAM. If there is a data mismatch, a P160A (Vehicle Options Reconfiguration Error) DTC is set. The new data will not be accepted unless a service tool is used to execute a "learn" command. This allows a service technician to ensure that the vehicle uses the proper configuration data after a BCM or PCM repair. Once a "learn" command is executed, the PCM will accept the next valid VIN, tire, axle and CCC data, store it into NVRAM, and perform and OBD-II code clear which resets all diagnostic data.
The flow charts below describe the process.