Circuit Description
The body control module (BCM) monitors the ACCESSORY signal from the ignition switch. When the vehicle operator places the ignition switch in the Accessory or Run position, the switch supplies B+ to the BCM ACCESSORY input terminal. If this circuit becomes shorted to B+, ground or the circuit opens, DTC B1380 will set.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B1380 Device Ignition ACCESSORY Circuit
DTC Symptom | DTC Symptom Descriptor |
|---|---|
01 | Short to Battery |
02 | Short to Ground |
04 | Open |
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 ACCESSORY voltage circuit when the ignition switch is in RUN or CRANK. |
| • | The BCM detects a short to battery or an open in the ACCESSORY 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 ACCESSORY circuit. Refer to Testing for Intermittent Conditions and Poor Connections .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This tests the ignition switch for a short circuit between the 12-volt reference supply circuit and the ACCESSORY circuit in the OFF position.
-
This tests the wiring of the ACCESSORY circuit for a short to ground or voltage.
-
This tests the ignition switch for a closed circuit between the ignition switch 12-volt reference supply circuit and the ACCESSORY circuit in the Run and Accessory switch positions. Care must be taken as the engine may crank during this test.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Body Control System Schematics and Power Distribution Schematics Connector End View Reference: Master Electrical Component List | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Does the scan tool display DTC B1380 as current? | -- | Go to Step 3 | Go to Diagnostic Aids |
Did you find a short between the 2 circuits? | B+ | Go to Step 4 | Go to Step 5 | |
Did you find and correct the condition? | B+ | Go to Step 9 | Go to Step 7 | |
|
Important: The engine may crank during this procedure.
Can you measure continuity in both the Run and Accessory positions? | -- | Go to Step 8 | Go to Step 6 | |
6 | Test the accessory and the ignition switch 12-volt reference supply terminals of the ignition switch harness connector, for intermittent or poor connections, and an open condition. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 7 |
7 | Replace the ignition switch. Refer to Ignition and Start Switch Replacement . Did you complete the replacement? | -- | Go to Step 9 | -- |
8 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 9 | -- |
9 |
Does the DTC reset? | -- | Go to Step 1 | System OK |
