An Air Bag code 42 is:
LH Crash Sensor Feed/Return Circuit Open
Normal Operation
The voltage at pin C20a - 18, circuit 31S - MA25 (BK/GN) is set by the air bag diagnostic monitor to be slightly less than battery voltage. Circuit 31S - MA25 (BK/GN) is connected to circuit 7 - MA28 (YE/RD) inside the LH crash sensor. Therefore, the voltage at circuit 7 - MA28 (YE/RD) and air bag diagnostic monitor pin C20a - 6 should be the same as the voltage at the air bag diagnostic monitor pin C20a - 18, circuit 31S - MA25 (BK/GN).
The air bag diagnostic monitor periodically pulls the voltage at pin C20a - 18, circuit 31S - MA25 (BK/GN), low to verify the connection to pin C20a - 6, circuit 7 - MA28 (YE/RD). If the voltage at pin C20a - 6, circuit 7 - MA28 (YE/RD), does not pull low as a result of this test, the air bag diagnostic monitor will flash diagnostic trouble code (DTC) 42 on the air bag indicator.
Possible Causes
Failure to get low voltage at air bag diagnostic monitor pin C20a - 6, circuit 7 - MA28 (YE/RD) during the test can be caused by:
1. An open circuit in the wiring harness in either circuit 31S - MA25 (BK/GN) or circuit 7 - MA28 (YE/RD).
2. An open circuit inside LH crash sensor across circuit 31S - MA25 (BK/GN) or circuit 7 - MA28 (YE/RD).
3. A short to battery or ignition voltage in any of the circuits 31S - MA26 (BK/RD), 31S - MA25 (BK/GN), 7 - MA30 (YE/GN), 7 - MA28 (YE/RD).
