Circuit Description
The body control module (BCM) monitors the ignition inputs Off/Run/Crank, 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. A fuse protected B+ voltage source is supplied by the BCM to the ignition switch over a discrete circuit. The ignition switch uses this voltage for accessory signal discrimination. The accessory signal is also routed to the vehicles electronic control unit (ECU) and is used as a digital signal reference.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC B1382 Device Ignition ACCESSORY Circuit Low |
| • | DTC B1383 Device Ignition ACCESSORY Circuit High |
| • | DTC B1384 Device Ignition ACCESSORY Circuit Open |
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
DTC B1382
The BCM detects that the accessory signal is shorted to ground for more than 10 seconds in the current ignition cycle.
DTC B1383
The BCM detects that the accessory signal is shorted to B+ for more than 10 seconds in the current ignition cycle.
DTC B1384
The BCM does not detect the accessory signal 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 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.
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This tests the ignition switch for a short circuit between the B+ 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 test may be expedited using the DTC to direct the testing. DTC B1382 short to ground or DTC B1383 short to voltage.
-
This tests the ignition switch for a closed circuit between the B+ supply circuit and the accessory circuit.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Body Control System Schematics Connector End View Reference: Power and Grounding Connector End Views and Master Electrical Component List | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 |
Does the scan tool display DTC B1382 to DTC B1384 as current? | Go to Step 3 | Go to Diagnostic Aids |
Did you find a short between the two circuits? | Go to Step 4 | Go to Step 5 | |
Did you find and correct the condition? | Go to Step 9 | Go to Step 7 | |
Can you measure continuity? | Go to Step 8 | Go to Step 6 | |
6 | Test the accessory and the ignition switch B+ 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 |
