For 1990-2009 cars
Body Control Module Components
Body Control System Schematics

### Circuit Description

CKT 28 is an input to the body control module (BCM). The BCM monitors CKT 28 in order to determine if the horn circuit is shorted to battery. When CKT 28 is shorted to battery for 0.5 seconds the BCM sets DTC B2753.

### Conditions for Setting the DTC

All of the following conditions must be met:

• | The CKT 28 is shorted to battery and the BCM is commanding the horn relay ON.

• | The system voltage must be between 9-16 volts.

• | The above conditions must be met for 0.5 seconds.

### Action Taken When the DTC Sets

The BCM stores DTC B2752 in the memory.

### Conditions for Clearing the MIL/DTC

• | A current DTC clears after the next fault free ignition cycle.

• | A history DTC clears after 100 consecutive ignition cycles without a fault present.

• | Clear history and the current DTC using a Scan Tool .

### Diagnostic Aids

• | If the DTC is a history DTC, the problem may be intermittent. Perform the above tests while wiggling the wiring and connectors. This will often cause the malfunction to appear.

• | Using a J 39200 Digital Multimeter, compare the scan tool values to the actual BCM values.

• | Perform a visual inspection of the wiring and connectors

### Test Description

The numbers below refer to the numbers on the diagnostic table.

1. This step tests the horn relay for proper operation.

2. This step tests CKT 28 for a short to battery within the underhood wiring harness junction block.

3. This step determines if a short to battery exists in CKT 28, between the underhood wiring harness junction block and the Body Control Module (BCM).

4. This step determines if a short to battery exists in the turn/headlamp switch assembly.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Important: A short to ground will cause an open fuse(s). Before performing this diagnostic procedure, inspect the fuse(s) for an open.
1 | Was the Body Control Module (BCM) System Check performed? | -- | Go to Step 2 | Go to Body Control Module System Check
2 | Replace the horn relay with a known good relay on the underhood wiring harness junction block. Use the Scan Tool in order to enable the horn relay. Does the horn work properly? | -- | Go to Step 10 | Go to Step 3
3 |

1. Disconnect the horn relay on the underhood wiring harness junction block.
2. Disconnect the underhood wiring harness junction block connector C3.
3. Use the J 39200 Digital Multi-Meter to measure the voltage in CKT 28 between the underhood wiring harness junction block connector C3 terminal C12 and ground.

Is the measured voltage equal to the specified value?

0V

Go to Step 5

Go to Step 4

4 | Replace the underhood wiring harness junction block. Refer to Underhood Fuse Block Replacement in Engine Electrical. Is the circuit repair complete? | -- | Go to Step 10 | --
5 |

1. Disconnect the BCM connector C1.
2. Disconnect the turn/headlamp switch assembly connector C1.
3. Use the J 39200 DMM to measure the voltage in CKT 28 between the BCM harness connector C1 terminal A4 and ground.

Is the measured voltage equal to the specified value?

0V

Go to Step 7

Go to Step 6

6 | Repair the short to battery positive in CKT 28 between the BCM connector C1 terminal A4, the underhood wiring harness junction block connector C3 terminal C12 and the turn/headlamp switch assembly connector C1 terminal A. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 10

--

7 | Use the J 39200 DMM in order to measure the voltage in CKT 28 between the turn/headlamp switch assembly connector C1 terminal A and ground. Is the measured voltage equal to the specified value? | 0 V | Go to Step 9 | Go to Step 8
8 | Replace the turn/headlamp switch assembly. Is the repair complete? | -- | Go to Step 10 | --
9 | Replace the BCM. Refer to the following procedures:

• | Body Control Module (BCM) Programming/RPO Configuration

• | Body Control Module (BCM) Replacement.

Is the repair complete?

--

Go to Step 10

--

10 | Clear the DTCs from the memory. Are the DTCs cleared from the memory? | -- | Go to Body Control Module System Check | --