Electronic Brake CNTRL Module (EBCM) - PCM Class II Serial Data

The PCM uses the Class 21 serial data line to receive rough road information from the EBCM. 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 EBCM calculates rough road information by monitoring the ABS wheel speed sensors. If a malfunction occurs which does not allow the 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 communication occurs which causes the PCM to not receive rough road information while a misfire DTC is requesting the MIL, DTC P1381 will set.