Circuit Description
The body control module (BCM) supplies battery positive voltage to the center high mounted stop lamp (CHMSL) through the stop lamp supply voltage circuit when the brakes are applied. The stop lamp supply voltage circuit also supplies a signal to the powertrain control module (PCM) or engine control module (ECM) and the electronic brake control module (EBCM) for other functions, is a separate pin in the BCM connector, and is internally connected within the BCM.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B3445 Stop Lamp Circuit
Conditions for Running the DTC
| • | The battery voltage must be between 9-16 volts. |
| • | The brake pedal must be applied. |
Conditions for Setting the DTC
| • | When the BCM detects a short to ground in the stop lamp supply voltage circuit to the CHMSL. |
| • | When the BCM never detects an open, indicating a BCM fault. |
| • | When the BCM detects a short to ground in the stop lamp supply voltage circuit to another module. |
Action Taken When the DTC Sets
The CHMSL 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 . |
| • | A short to ground in either stop lamp supply voltage circuits (CHMSL or other module) may cause this DTC. |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Exterior Lights Schematics Connector End View Reference: Master Electrical Component List | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 |
Does the center high mounted stop lamp (CHMSL) illuminate? | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 |
3 | Test for a short to ground in the stop lamp supply voltage circuit of the CHMSL. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 6 | Go to Step 4 |
4 | Test for a short to ground in the stop lamp supply voltage circuit of the other modules connected to this circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 6 | Go to Step 5 |
5 | Replace the body control module (BCM). Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 6 | -- |
6 |
Does the DTC reset? | Go to Step 2 | System OK |
