• | 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 |
---|---|---|---|---|
Daytime Running Lamp Relay B+ | 1 | 1 | -- | -- |
Headlamp LO/HID Relay B+ | 1 | 1 | -- | -- |
High Beam Relay B+ | 1 | 1 | -- | -- |
Ambient Light Sensor Signal Circuit | B2645 03 | B2645 07 | B2645 07 | -- |
Headlamp Flash to Pass Signal | 4 | 4 | 4 | -- |
Headlamp Dimmer Switch Signal | 4 | 4 | 4 | -- |
Daytime Running Lamp Relay Control | 3 | 3 | B2600 00 | -- |
Headlamp Low Beam Control | 1 | 1 | 1 | -- |
Headlamp Low Beam Relay Control | 1 | 1 | B2575 00 | -- |
Headlamp Switch Off Control | B257A 00 | 2 | 2 | -- |
Headlamp Switch On Control | B257A 00 | 1 | 1 | -- |
Headlamp High Beam Control | 1 | 1 | 1 | -- |
Headlamp High Beam Relay Control | 1 | 1 | B2580 00 | -- |
Park Lamp Switch On Control | B257A 00 | B257A 00 | 2 | -- |
Ambient Light Sensor Ground Circuit | -- | B2645 07 | -- | -- |
Headlamp Switch Ground | -- | 2 | -- | -- |
Turn Signal/Multifunction Switch Malfunction | -- | 4 | -- | -- |
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When the headlamp and panel dimmer 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 and panel dimmer switch headlamps ON signal circuit and the park lamp switch signal circuit are both open and have no ground signal. When the headlamp and panel dimmer 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 test normal, replace the headlamp and panel dimmer switch. |
⇒ | If the test lamp is always ON, test the signal circuit for a short to ground. If the circuit test normal, replace the headlamp and panel dimmer 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 test normal, replace the headlamp and panel dimmer switch. |
⇒ | If the test lamp is always ON, test the signal circuit for a short to ground. If the circuit test normal, replace the headlamp and panel dimmer switch. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for BCM replacement, setup, and programming |