B1380

DTC B1380

CIRCUIT DESCRIPTION
The body control module (BCM), monitors the ignition inputs Off, Ignition 3 Crank and Ignition 1 supplied from the ignition switch. The BCM uses the sequence that the signals appear and their voltage levels to determine the cower mode called for by the vehicle operator using the ignition switch A 12 Volt reference voltage is supplied by the BCM to the ignition switch over a discrete circuit. The ignition switch uses this voltage for power mode signal discrimination. When the operator places the Ignition switch in the Run or Accessory position, the ignition 3 circuit delivers the signal to the BCM.

CONDITIONS FOR RUNNING THE DTC
- The BCM must be powered and must detect a change in the ignition switch circuit states.
- The vehicles battery must be fully charged.

CONDITIONS FOR SETTING THE DTC
The BCM detects that the Ignition 3 signal is shorted to Ground, Voltage or open for more than 10 seconds in the current ignition cycle

ACTION TAKEN WHEN THE DTC SETS
- The BCM stores DTC to 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 clears on the next malfunction free cycle.
- A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

DIAGNOSTIC AIDS
A history DTC maybe caused by an intermittent short or open in the Ignition 3 circuit.

TEST DESCRIPTION

Steps 1 - 2:

Steps 3 - 9:

The numbers below refer to the step numbers on the diagnostic table.
3. This tests the ignition switch for a short circuit between the 12 Volt reference supply circuit and the Ignition 3 circuit in the Off position.
4. This tests the wiring of the Ignition 3 circuit for a short to Ground or Voltage.
5. This tests the ignition switch for a closed circuit between the ignition switch 12 Volt reference supply circuit and the Ignition 3 circuit in the Run and Crank switch positions. Care must be taken as the engine may crank during this test.