Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Flash to Pass Switch Signal | 1 | 1 | 1 | -- |
Headlamp High Beam Relay Control | B2580 06 | B2580 06 | B2580 01 | -- |
Headlamp Low Beam Relay Control | 1 | 1 | 1 | -- |
Headlamp Switch High Beam Signal | 1 | 1 | 1 | -- |
Headlamp Switch Headlamps On Signal | 1 | 1 | 1 | -- |
Headlamp Switch Headlamps Off Signal | 1 | 1 | 1 | -- |
LF High Beam Headlamp Voltage Supply | 1 | 1 | 1 | -- |
LF Low Beam Headlamp Voltage Supply | 1 | 1 | 1 | -- |
RF High Beam Headlamp Voltage Supply | 1 | 1 | 1 | -- |
RF Low Beam Headlamp Voltage Supply | 1 | 1 | 1 | -- |
LF Headlamp Ground | -- | 1 | 1 | -- |
RF Headlamp Ground | -- | 1 | 1 | -- |
Turn Signal/Multifunction Switch Ground | -- | 1 | 1 | -- |
1. Headlamps Malfunction | ||||
Circuit/System Description
The ambient light sensor is a light sensitive transistor that varies the voltage signal to the HVAC control module. The HVAC control module sends a signal to the body control module (BCM) via class 2 serial data commanding the BCM to apply ground to the headlamp low beam relay control circuit. This energizes the low beam relay, closing the switched side and applies battery voltage to the LEFT and RIGHT LOW BEAM fuses. Battery voltage is applied from the low beam fuses, through the low beam voltage supply circuits to the ballast in the headlamp assembly illuminating the headlamps. The BCM also sends a message via class 2 serial data to the instrument panel cluster (IPC) requesting the lights on indicator be illuminated. For more detailed information concerning headlamp operation refer to Exterior Lighting Systems Description and Operation .
Diagnostic Aids
This diagnostic procedure assumes that the headlamps operate as described in Exterior Lighting Systems Description and Operation .
Reference Information
Schematic Reference
Connector End View Reference
Displays and Gages Connector End Views
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
Ignition ON, with a scan tool perform the display test for the IPC and observe the lights on indicator.
| ⇒ | If the lights on indicator illuminates during the test, replace the BCM. |
| ⇒ | If the lights on indicator does not illuminate during the test or remains illuminated at all times, replace the IPC. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for BCM or IPC replacement, setup, and programming
