For 1990-2009 cars

### Circuit Description

The body control module (BCM) receives a ground signal from the door jamb or dome lamp switches requesting courtesy/dome lamp illumination. When this occurs, the BCM directly sends a voltage through the inadvertent power supply voltage circuit illuminating the courtesy/dome lamps.

### DTC Descriptors

This diagnostic procedure supports the following DTCs:

• | DTC B2557 Passenger Compartment Lamp Control Circuit Low

• | DTC B2558 Passenger Compartment Lamp Control Circuit High

### Conditions for Running the DTC

The battery voltage must be between 9-16 volts.

### Conditions for Setting the DTC

• | When the BCM receives a courtesy lamp illumination request signal and the inadvertent power supply voltage circuit is shorted to ground

• | When the BCM is not receiving a courtesy lamp illumination request signal and the inadvertent power supply voltage circuit is shorted to voltage

• | There is a loss of the underhood fuse block truck body controller (TBC) battery supply voltage to the BCM for more than 1 second.

### Action Taken When the DTC Sets

The courtesy/dome lamps will not operate or are always ON.

### Conditions for Clearing the MIL/DTC

• | This DTC will clear on current status after the condition for setting the fault is corrected.

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

• | History and current DTCs can be cleared using a scan tool.

### Diagnostic Aids

Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent Conditions and Poor Connections .

### Test Description

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

1. This step determines if the problem exists in the wiring.

2. This step determines if a condition exist in the TBC battery voltage supply circuit.

3. After replacement of the BCM, you must calibrate the new module for proper operation.

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Interior Lights Schematics Connector End View Reference: Lighting Systems Connector End Views or Data Communication Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Test the inadvertent power supply voltage circuit for a short to voltage or short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 6 | Go to Step 3
3 | Test the truck body controller (TBC) battery positive supply voltage circuit for a short to ground, open, or high resistance. Refer to Circuit Testing . Did you find and correct the condition? | Go to Step 6 | Go to Step 4
4 | Inspect for poor connections at the harness connectors of the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 6 | Go to Step 5
5 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 6 | --
6 |

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 the DTC reset?

Go to Step 2

System OK