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

### Circuit Description

Circuit 439 is the ignition 1 positive voltage circuit input to the body control module (BCM) from the ignition switch. When the BCM senses that ignition 1 is open, DTC B1372 is set.

### Conditions for Running the DTC

• | The engine is on.

• | At least 20 seconds has elapsed since the engine was started.

### Conditions for Setting the DTC

The ignition 1 input is inactive after the engine has been running for 20 seconds.

### Action Taken When the DTC Sets

• | The SERVICE VEHICLE SOON indicator illuminates.

• | The check gauges chime sounds.

### Conditions for Clearing the DTC

• | A current DTC B1372 will clear when the code setting condition is no longer present and the ignition switch is cycled.

• | All BCM history codes will clear after 100 ignition cycles (from OFF to ON) with no current codes active during the 100 ignition cycles.

### Diagnostic Aids

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

### Test Description

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

1. This step determines if CKT 439 is shorted to ground.

2. This step determines if the BCM is internally shorted.

3. This step determines if voltage is supplied from the battery to the A/C BFC fuse.

Step | Action | Yes | No
--- | --- | --- | ---
1 | Did you perform the Body Control System Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Body Control System
2 |

1. Install a Scan Tool.
2. Turn ON the ignition, leaving the engine OFF.
3. With the Scan Tool, observe the IGNITION 1 INPUT data parameter in the BCM data list.

Does the scan tool display ACTIVE?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3 | Inspect the A/C BFC fuse. Is the fuse open? | Go to Step 4 | Go to Step 6
4 |

1. Connect a test lamp between the A/C BFC fuse terminals at the underhood junction block.
2. Turn ON the ignition, leaving the engine OFF.

Does the test lamp illuminate?

Go to Step 5

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

5 |

1. Turn OFF the ignition.
2. Disconnect the BCM connector containing the ignition 1 positive voltage circuit.
3. Turn ON the ignition, leaving the engine OFF.

Does the test lamp still illuminate?

Go to Step 8

Go to Step 10

6 |

1. Remove the A/C BFC fuse.
2. Turn ON the ignition, leaving the engine OFF.
3. Probe both fuse terminals for the ignition 1 positive voltage circuit at underhood junction block with a test lamp connected to ground.

Does the test lamp illuminate for one of the terminals?

Go to Step 7

Go to Step 9

7 | Test the ignition 1 positive voltage circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 12 | Go to Step 11
8 | Repair the short to ground in the ignition 1 positive voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? |  | --
9 | Repair the open in the ignition feed circuit to the A/C BFC fuse. Refer to Wiring Repairs in Wiring Systems. Did you complete the action? | Go to Step 12 | --
10 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 12 | Go to Step 11
11 | Replace the BCM. Refer to Body Control Module Replacement . Important: Peform the setup procedure for the body control module. Refer to Body Control Module (BCM) Programming/RPO Configuration . Did you complete the replacement? | Go to Step 12 | --
12 |

1. Use the Scan Tool in order to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does te DTC reset?

Go to Step 2

System OK