Circuit Description
The body control module (BCM) receives a variable voltage signal from the instrument panel (I/P) dimmer switch requesting to illuminate the instrument panel illumination lamps to a desired intensity. When this occurs, the BCM directly sends a pulse width modulated (PWM) voltage based on the I/P dimmer switch position through the instrument panel lamps dimming control circuit to the instrument panel illumination lamps.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2625 Display Dimming Pulse Width Modulation (PWM) Output Circuit
Conditions for Running the DTC
The battery voltage must be between 9-16 volts.
Conditions for Setting the DTC
| • | When the BCM receives a instrument panel lamps illumination request signal and the instrument panel lamps dimming control circuit is shorted to ground. |
| • | There is a loss of the rear fuse block truck body controller (TBC) 4 battery supply voltage to the BCM for more than 1 second. |
Action Taken When the DTC Sets
The instrument panel illumination lamps will not operate.
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 in Wiring Systems. |
| • | In the event that DTC B2625 and DTC B0951 are set at the same time, the diagnostic chart for diagnosing DTC B0951 must be followed first. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step test determines if the problem exists in the wiring or the BCM.
-
This step inspects for poor connections before a component is replaced.
-
After replacement of the BCM you must calibrate the new module for proper operation.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Interior Lights Dimming Schematics Connector End View Reference: Lighting Systems Connector End Views or Computer/Integrating Systems Connector End Views in Computer/Integrating Systems | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
Test the instrument panel lamps dimming control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 5 | Go to Step 3 | |
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 in Wiring Systems. Did you find and correct the condition? | Go to Step 5 | Go to Step 4 | |
Replace the BCM. Refer to Control Module References in Computer/Integrating Systems. Did you complete the replacement? | Go to Step 5 | -- | |
5 |
Does the DTC reset? | Go to Step 2 | System OK |
