B1374

DTC B1374

CIRCUIT DESCRIPTION
The body control module (BCM) monitors the ignition inputs Ignition Off/Run/Crank, Ignition 1 Run/Crank and the accessory signals supplied from the ignition switch. The BCM uses the sequence that the signals appear and their voltage levels to determine the power mode called for by the vehicle operator using the ignition switch. Battery voltage is supplied to the ignition switch by the IGN TRANSD fuse. The ignition switch uses this voltage for Run/Crank signal discrimination. The Ignition 1 Run/Crank signal also energizes the Run/Crank relay. If the BCM detects that the Ignition 1 Run/Crank signal circuit is open or shorted, one of the following DTCs will set:

DTC DESCRIPTORS
- DTC B1372 Device Ignition 1 (ON and START) Circuit Low
- DTC B1373 Device Ignition 1 (ON and START) Circuit High

CONDITIONS FOR RUNNING THE DTC
- The BCM detects a change in the ignition switch circuit states.
- Battery voltage is 9.0-18.5 Volts.

CONDITIONS FOR SETTING THE DTC

DTC B1372
The BCM detects that the Ignition 1 Run/Crank signal is open or shorted to ground for at least 10 seconds.

DTC B1373
The BCM detects that the Ignition 1 Run/Crank signal is shorted to voltage for at least 10 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The BCM stores DTC B1372 or B1373 in memory.
- The BCM operates in a fail-safe power mode dependent on the last valid power mode detected and the state of the engine run flag data on the class 2 serial data communications circuits.
- The other modules on the vehicle operate in a fail safe power mode dependent on the last valid power mode transmitted by the BCM and the state of the engine run flag on the class 2 serial data communications circuits.

CONDITIONS FOR CLEARING THE DTC
- A current DTC B1372 or B1373 is moved to history when the ignition is cycled.
- A history DTC B1372 or B1373 clears when the ignition has been cycled 100 times, without a repeat of the malfunction.

TEST

Steps 1 - 4:

Steps 5 - 8:

Steps 9 - 14: