EBTCM / EBCM - PCM Class 2 Serial Data

The PCM uses the Class 2 serial data line to communicate with various other components and systems within the vehicle. The PCM ensures that communication remains established by monitoring the Class 2 serial data circuit for state of health messages from the other devices using the circuit. If the PCM detects a loss of the state of health serial data message from the Electronic Brake and Traction Control Module (EBTCM), the PCM will store DTC P1602.

The PCM also receives rough road information from the EBTCM / EBCM on the Class 2 serial data circuit. The PCM uses the rough road information to enhance the misfire diagnostic by detecting crankshaft speed variations caused by driving on rough road surfaces. This allows false misfire information to be rejected. The EBTCM / EBCM calculates rough road information by monitoring the ABS wheel speed sensors. If a malfunction occurs which does not allow the EBTCM / EBCM to transmit correct rough road information to the PCM while a misfire DTC is requesting the MIL, DTC P1380 will set. If a loss of communications occurs which causes the PCM to not receive rough road information while a misfire DTC is requesting the MIL, DTC P1381 will set.

Under certain conditions, the PCM has the ability to request the EBTCM to shut OFF traction control via Class 2 serial data. The following DTCs will cause traction control to be disabled, an ABS/TCS DTC to be set, and the Traction OFF lamp to be illuminated:
^ DTC P0101 - Mass Air Flow System Performance
^ DTC P0102 - Mass Air Flow Sensor Circuit Low Frequency
^ DTC P0103 - Mass Air Flow Sensor Circuit High Frequency
^ DTC P0171 - Fuel Trim System Lean
^ DTC P0172 - Fuel Trim System Rich
^ DTC P0300 - Engine Misfire Detected
^ DTC P0336 - 18x Reference Signal Circuit
^ DTC P0341 - Camshaft Position Sensor Performance
^ DTC P1200 - Injector Control Circuit
^ DTC P1374 - 3X Reference Circuit

Refer to ABS/TCS in Antilock Brake System and Traction System for information regarding ABS/TCS operation.

For information concerning the various devices that use the Class 2 serial data circuit, refer to Serial Data in Electrical Diagnosis.