• | 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. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
HDM Relay Fuse B+ | 1 | 1 | -- | -- |
HI HEADLAMP relay B+ | 2 | 2 | -- | -- |
IGN COILS Relay Fuse B+ | 2 | 2 | -- | -- |
DRL Defeat Switch Signal | 3 | 3 | 3 | -- |
Headlamp High Beam Switch Signal | 4 | 4 | 4 | -- |
Headlamp Flash to Pass Switch Signal | 4 | 4 | 4 | -- |
Headlamp ON Switch Signal | 3 | 3 | 3 | -- |
Low Beam Headlamp Relay Control | B2575 00 | B2575 00 | B2575 00 | -- |
Headlamp ON Indicator Control | B3802 00 | 3 | 3 | -- |
High Beam Headlamp Relay Control | B2580 00 | B2580 00 | B2580 00 | -- |
Low Beam Headlamp Control | 1 | 1 | 1 | -- |
High Beam Headlamp Control | 2 | 2 | 2 | -- |
Headlamp ON Indicator Low Reference | 3 | 3 | 3 | -- |
HDM Relay Ground | -- | 1 | -- | -- |
Headlamp Switch Ground | -- | 3 | -- | -- |
Turn Signal/Multifunction Switch Ground | -- | 4 | -- | -- |
Left Headlamp Ground | -- | 1 | -- | -- |
Right Headlamp Ground | -- | 1 | -- | -- |
1. Headlamp Malfuntion - Low Beam 2. Headlamp Malfuntion - High Beam 3. Headlamp Switch Malfunction 4. Turn Signal/Multifunction Switch Malfunction |
The HDM and high beam relay receive battery voltage directly from the battery. The BCM supplies a 100% duty cycle PWM ground signal to the HDM for automatic low beam headlamp control and normal low beam headlamp operation. The BCM also supplies ground to the high beam relay coil for high beam headlamp operation. When the driver places the headlamp switch in the HEADLAMP position and the dimmer switch is in the low beam position, the HDM switches to full output sending current flow through the left and right low beam headlamp fuses to both low beam headlamps. The dimmer switch sends a ground signal to the BCM in the high beam position and a momentary ground signal in the flash-to-Pass (FTP) position from G102 to deactivate the low beam headlamps and activate the high beam headlamps. With the headlamps in the low beam position, the high beams may be momentarily turned on or flashed by activating the FTP portion of the switch.
Headlights/Daytime Running Lights (DRL) Schematics
Exterior Lighting Systems Description and Operation
Control Module References for scan tool information
⇒ | If the parameter does not cycle between the specified values, refer to the Headlamp Switch Malfunction. |
⇒ | If 1 or both of the low beam headlamps do not turn ON and OFF, refer to the Low Beam Headlamp Malfunction. |
⇒ | If the parameter does not cycle between the specified values, refer to the Turn Signal/Multifunction Switch Malfunction. |
⇒ | If 1 or both of the high beam headlamps do not turn ON and OFF, refer to the High Beam Headlamp Malfunction. |
⇒ | If the HI Beam Headlamps do not turn ON and OFF between the commanded states, refer to Turn Signal/Multifunction Switch Malfunction. |
⇒ | If the indicator does not turn ON and OFF, refer to High Beam Indicator Malfunction. |
⇒ | If the test lamp does not illuminate, test the ground circuit for an open/high resistance. |
⇒ | If not the specified value, test the headlamp ON switch signal circuit terminal D for a short to ground. If the circuit tests normal, replace the BCM. |
⇒ | If not the specified value, test the headlamp ON switch signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM. |
⇒ | If the test lamp does not illuminate, test the ground circuit for an open/high resistance. |
⇒ | If not the specified value, test the high beam switch signal circuit terminal C for a short to ground. If the circuit tests normal, replace the BCM. |
⇒ | If not the specified value, test the flash to pass switch signal circuit terminal B for a short to ground. If the circuit tests normal, replace the BCM. |
⇒ | If not the specified value, test the high beam switch signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM. |
⇒ | If not the specified value, test the flash to pass switch signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM. |
⇒ | If the test lamp does not illuminate, test the ground circuit for an open/high resistance. |
⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. |
⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, and the B+ circuit fuse is open, test the control circuit terminal 4 for a short to ground. |
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
⇒ | If the headlamps are always OFF, test the control circuit for a short to ground or an open high resistance. |
⇒ | If the headlamps are always ON, test the control circuit for short to voltage. |
⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM. |
⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM. |
⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. |
⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
⇒ | If the test lamp does not illuminate, test the ground circuit for an open/high resistance. |
⇒ | If the high beam headlamps do not activate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the inoperative high beam headlamp. |
⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM. |
⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM. |
Ignition ON, with a scan tool perform the Display Test for the instrument panel cluster (IPC) and observe the high beam indicator.
⇒ | If the high beam indicator illuminates during the test, replace the BCM. |
⇒ | If the high beam indicator does not illuminate during the test or remains illuminated at all times, replace the IPC. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for BCM replacement, setup, and programming |