Computer/Integrating System Diagnosis
DTC B1370
DTC DESCRIPTORS
DTC B1370 01
Device Ignition 1 ON and START Circuit Short to Battery
DTC B1370 06
Device Ignition 1 ON and START Circuit Open
DIAGNOSTIC FAULT INFORMATION
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Testing and Inspection
TYPICAL SCAN TOOL DATA
Ignition Run/Crank - BCM:
Refer to Power Mode Description and Operation for other power mode parameters.
CIRCUIT/SYSTEM DESCRIPTION
As the power mode master (PMM), the body control module (BCM) monitors the ignition inputs off/run/crank voltage, ignition 1 voltage and the accessory voltage signals supplied from the ignition switch. The BCM uses the sequence that the signals appear, their voltage levels, the engine run flag (ERF) status and the remote start status to determine the power mode.
When the ignition switch is placed in the RUN or CRANK position, the switch supplies B+ to the BCM ignition 1 voltage input terminal.
CONDITIONS FOR RUNNING THE DTC
B1370 01
Ignition switch is in the OFF or ACC positions.
B1370 06
Ignition switch is in the START position.
CONDITIONS FOR SETTING THE DTC
B1370 01
Ignition 1 voltage circuit is shorted to voltage for more than 2 seconds.
B1370 06
- Ignition 1 voltage circuit is open for more than 2 seconds.
- Ignition 1 voltage, accessory voltage, or off/run/crank voltage circuit shorted to ground.
- Battery positive voltage circuit of the ignition switch open or shorted to ground.
- Run crank relay coil control circuit open (including relay coil and ground).
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
Use the DMM MIN/MAX function to capture/locate intermittent conditions.
A short to ground on any ignition switch output circuit will open the BCM fuse.
If the ignition 1 voltage circuit is shorted to voltage the engine may continue to run and the service engine soon lamp will remain on with the ignition key removed
CIRCUIT/SYSTEM TESTING
1. Ignition OFF.
- If the ignition will not return to the OFF position, disconnect BCM C 1 and proceed to step 5.
2. Verify the scan tool Ignition Run/Crank parameter is Inactive.
- If the parameter is Active, test the ignition 1 voltage circuit for a short to voltage. If the circuit tests normal, test or replace the ignition switch.
3. Ignition RUN, verify the scan tool Ignition Run/Crank parameter is Active.
- If the parameter is Inactive, test the ignition 1 voltage circuit for an open/high resistance. If the circuit tests normal, proceed to the next step.
4. Ignition OFF, disconnect BCM connector C 1.
5. Ignition RUN, verify that a test lamp illuminates between the ignition 1 voltage circuit and ground.
- If the test lamp does not illuminate, test the off/run/crank voltage, accessory voltage, and ignition 1 voltage circuits of the ignition switch for a short to ground. If the circuits test normal, test the battery positive voltage circuit of the ignition switch for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the ignition switch.
6. Ignition OFF, disconnect BCM connector C 4.
7. Measure for battery voltage between the run crank relay coil control circuit terminal and a battery positive voltage circuit.
- If less than battery voltage, disconnect the IGN MAIN PCB relay and check the run crank relay coil control and ground circuits of the IGN MAIN PCB relay for an open/high resistance. If the circuits test normal, test or replace the relay.
8. If all circuits test normal and the DTC is current, replace the BCM.
REPAIR INSTRUCTIONS
Perform the Diagnostic Repair Verification after completing the repair. Verification Tests
- Control Module References for BCM replacement, setup, and programming
- Ignition Switch Replacement.