Circuit Description
The body control module (BCM) grounds both high beam headlamp relay coils at terminal C8, energizing the relays, when the BCM receives an input to turn the high beam lamps ON. This places both high beam headlamps, that were in a series circuit, in a parallel circuit by providing a separate ground path for each headlamp. This configuration allows the high beam headlamps to illuminate at full intensity.
Conditions for Setting the DTC
The BCM monitors output to the high beam relays every second at terminal C8. The fault code is set when the commanded state doesn't match the feedback for 2 seconds (open circuit, short to ground or B+).
Action Taken When the DTC Sets
| • | The BCM continues to command the state requested until the state is achieved or until the state changes. |
| • | The BCM stores a DTC B2473 in the BCM memory. |
Conditions for Clearing the DTC
| • | The conditions for the fault are no longer present. |
| • | Use of a scan tool. |
| • | A history DTC will clear after 50 ignition cycles if the condition for the fault is no longer present. |
Diagnostic Aids
Refer to Power and Grounding Component Views in Wiring Systems for an end view and for terminal assignments of the relay box when the diagnostics direct you to take electrical measurements at the relay box.
Test for the following conditions if a history or intermittent DTC is indicated:
| • | A damaged wiring harness. Inspect the wiring harness for damage. If the wiring harness appears to be in good condition, observe the display on the DMM while moving the connectors and wiring harnesses related to the circuits. A change in the DMM display during this test will indicate the location of the fault. |
| • | For additional information, refer to Intermittents and Poor Connections Diagnosis . |
| • | A short to ground in the circuit may cause the high beam indicator bulb, located in the instrument cluster, along with one or both high beam headlamps to illuminate at all times. |
Test Description
The following numbers refer to the step numbers on the diagnostic table:
-
This step uses a scan tool to test the high beam operation and to verify if the fault is present.
-
This step tests for an intermittent condition in the circuits that can cause a DTC B2473 to set.
-
After verifying that no circuit problems exist, the BCM is most likely at fault. The BCM needs to be programmed after installation.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the BCM System Check? | -- | Go to Step 2 | |
Did the high beam lamps light when commanded ON? | -- | Go to Step 3 | Go to Step 4 | |
3 | Did the high beam lamps go OFF when commanded with the scan tool? | -- | Go to Step 6 | Go to Step 7 |
4 |
Was an open circuit found? | -- | Go to Step 8 | Go to Step 5 |
5 | Measure the voltage at terminal C8. Is the measured voltage at the specified value? | B+ | Go to Step 6 | Go to Step 10 |
Is the repair complete? | -- | Go to Step 12 | -- | |
7 | Measure the resistance from BCM connector C2 terminal C8 to a good ground. Is the measured resistance at the specified value? | OL | Go to Step 12 | Go to Step 9 |
8 | Locate and repair the open circuit in CKT M60. Is the repair complete? | -- | Go to Step 12 | -- |
9 | Locate and repair the short to ground in the high beam relay control circuit. Is the repair complete? | -- | Go to Step 12 | -- |
10 | Locate and repair the short to B+ in the high beam relay control circuit. Is the repair complete? | -- | Go to Step 12 | -- |
|
Important: Perform the set up procedure for the BCM. Replace the BCM. Refer to Body Control Module Replacement . Is the replacement complete? | -- | Go to Step 12 | -- | |
12 |
Did a current DTC B2473 set? | -- | Go to Step 2 | System OK |
