• | 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 |
---|---|---|---|---|
HDLP LO/HID Relay B+ | 1 | 1 | 1 | -- |
HI Beam Relay B+ | 1 | 1 | 1 | -- |
Flash to Pass Switch Signal | 1 | 1 | 1 | -- |
Headlamp Switch Headlamps ON Signal | B257A 00 | 1 | 1 | -- |
Headlamp Switch Headlamps OFF Signal | B257A 00 | 1 | 1 | -- |
Headlamp Switch High Beam Signal | 1 | 1 | 1 | -- |
Headlamp High Beam Relay Control | 1 | 1 | B2580 00 | -- |
Headlamp Low Beam Relay Control | 1 | 1 | B2575 00 | -- |
Headlamp and Panel Dimmer Switch Ground | -- | 1 | -- | -- |
LF Headlamp Ground | -- | 1 | -- | -- |
RF Headlamp Ground | -- | 1 | -- | -- |
Turn Signal/Multifunction Switch Ground | -- | 1 | -- | -- |
1. Headlamps Malfunction |
When the headlamp switch is placed in the AUTO position, the body control module (BCM) receives a ground signal through the headlamp switch headlamps OFF signal circuit. The headlamp switch headlamps ON signal circuit and the park lamp switch signal circuit are both open and have no ground signal. When the headlamp switch is placed in the PARK or HEAD position, the BCM will receive a ground signal through the headlamp switch headlamps ON signal circuit and the park lamp switch signal circuit. The headlamp switch headlamps OFF signal circuit will be open and have no ground signal.
Battery voltage must be between 9-16 volts.
DTC B257A 00 will set when the BCM detects a short to ground on the headlamp switch headlamps OFF signal circuit or the headlamp switch headlamps ON signal circuit.
• | When DTC B257A 00 is present on the headlamp switch headlamps OFF signal circuit, the low beam headlamps are always ON in the AUTO position. The headlamp switch operates in all positions other than AUTO. The AUTO headlamp defeat is inoperative. |
• | When DTC B257A 00 is present on the headlamp switch headlamps ON signal circuit, the low beam headlamps are always ON. The BCM disregards all headlamp switch inputs. |
• | The condition responsible for setting the DTC no longer exists. |
• | A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred. |
Headlights/Daytime Running Lights (DRL) Schematics
Exterior Lighting Systems Description and Operation
Control Module References for scan tool information
⇒ | If the test lamp is always OFF, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the headlamp switch. |
⇒ | If the test lamp is always ON, test the signal circuit for a short to ground. If the circuit tests normal, replace the headlamp switch. |
⇒ | If the test lamp is always OFF, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the headlamp switch. |
⇒ | If the test lamp is always ON, test the signal circuit for a short to ground. If the circuit tests normal, replace the headlamp switch. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for BCM replacement, setup, and programming |