For 1990-2009 cars

### Circuit Description

When the Body Control Module (BCM) receives an input to turn the high beam lamps On, the BCM in turn will ground both high beam headlamp relay coils through the high beam relays control circuit, energizing the relays. When the high beam relays energize, both high beam headlamps that were in a series circuit, now have a separate power and ground source for each high beam 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 . The fault code is set when the commanded state does not match the feedback for 2 seconds, open circuit, short to ground or B+. The fault code will not set if an open circuit occurs in the individual coil side feed of the high beam relays, or an open in the individual high beam relay control circuits.

### Action Taken When the DTC Sets

• | The BCM continues to command the state requested until it is achieved or until it changes.

• | Stores a DTC B2473 in the BCM memory.

### Conditions for Clearing the DTC

• | The high beam relays are pulled low when commanded ON.

• | The conditions for setting the DTC are no longer present.

• | A history DTC will clear after 50 consecutive malfunction free ignition cycles.

• | The BCM receives the clear code command from the scan tool.

### Diagnostic Aids

Refer to Power Distribution 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.

Check for the following conditions if a history or intermittent DTC is indicated:

• | A intermittent open, short to ground, or short to B+ in the high beam relay control circuit.

• | 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 Inducing Intermittent Fault Conditions in Wiring Systems.

• | 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:

1. This step uses a scan tool to test the high beam operation and to verify if the fault is present.

2. This step checks for a open in the BCM high beam relay control circuit.

3. After verifying that no circuit problems exist, the BCM is most likely at fault. The BCM needs to be programmed after installation.

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics
1 | Did you perform the Lighting System Diagnostic System Check? | Go to Step 2 | Go to Diagnostic Starting Point - Lighting Systems
2 |

1. Install the scan tool.
2. Turn the ignition switch ON, with the engine OFF.
3. Select HIGH BEAM from the Light Test Menu in Special Functions.
4. Press the ON button then press the OFF button and monitor HIGH BEAM parameters.

Do the high beam relays turn ON and OFF with each command?

Go to Diagnostic Aids

Go to Step 3

3 | Test the control circuit of the high beam relays for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 7 | Go to Step 4
4 | Test the control circuit of the high beam relays 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 7 | Go to Step 5
5 | Test the control circuit of the high beam relays for a short to B+. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 7 | Go to Step 6
6 | Important: Perform the programming procedure for the BCM. Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Is the replacement complete? | Go to Step 7 | --
7 |

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