B1370

DTC B1370

CIRCUIT DESCRIPTION
The body control module (BCM) monitors the ignition 1 signal from the ignition switch. When the vehicle operator places the ignition switch in the RUN or CRANK position, the switch supplies B+ to the BCM ignition 1 input terminal. If this circuit becomes shorted to B+, ground or the circuit opens, DTC B1370 will set.

DTC DESCRIPTOR




This diagnostic procedure supports the following DTC:
DTC B1370 Device Ignition 1 Circuit
This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description.

CONDITIONS FOR RUNNING THE DTC
Voltage supplied to the module is in the normal operating voltage range of 9-16 volts.

CONDITIONS FOR SETTING THE DTC
- The BCM detects a short to ground in the ignition 1 voltage circuit when the ignition switch is in RUN or CRANK.
- The BCM detects a short to battery or an open in the ignition 1 voltage circuit when the switch is in the OFF position.
- Any of the conditions above must be present for more than 10 seconds.

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 GMLAN 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 GMLAN serial data communications circuits.

CONDITIONS FOR CLEARING THE DTC
- A current DTC clears when the malfunction is no longer present.
- 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 may be caused by an intermittent short or open in the ignition 1 circuit. Refer to Testing for Intermittent Conditions and Poor Connections. Component Tests and General Diagnostics

TEST DESCRIPTION

Step 1 - Step 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 1 circuit in the OFF position.
4. This tests the wiring of the ignition 1 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 1 circuit in the Run and Crank switch positions. Care must be taken as the engine may crank during this test.