Drl only work in daytime not at night Headlight switch won't turn on headlights Fog lights work fine along with all other exterior lights
Drl only work in daytime not at night ???? Daytime running lamps are only suppose to work in day light hours . Low beam & high beams ? none of these work at night ?
Headlamps
The headlamps may be turned on in two different ways. First, when the driver places the headlamp switch in the HEADLAMP position, for normal operation. Second, with the headlamp switch placed in the AUTO position, for automatic lamp control (ALC). During ALC the headlamps will be in day time running lamp (DRL) operation in daylight conditions, or headlamp operation in low light conditions.
Headlamp ON/OFF control is determined by the body control module (BCM) by a signal on the headlamp switch on input circuit when the headlamp switch is in the HEAD position. When the headlamp switch is in the AUTO position, the BCM determines headlamps ON/OFF by the voltage from the ambient light sensor.
If the headlight switch is left in the ON position, the inadvertent power control feature will turn off the headlights approximately 10 minutes after the ignition switch is turned to the OFF position. If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, or if the ignition switch is in the ACCY position, the headlights will remain on until turned off or the battery runs dead.
The high beam indicator is illuminated when the instrument cluster receives a class 2 serial data message from the BCM that the high beams are illuminated.
Do you know what the BCM is ? Do you know what DTC'S - diagnostic trouble code's are ?
DTC B2575
When the body control module (BCM) senses a request for low beam headlamp illumination, the BCM sends a ground signal to the low beam headlamp relay through the headlamp low beam relay control circuit. The headlamp low beam relay will apply voltage to illuminate the headlamps.
Low and High Beams Headlamps Inoperative
Step
Action
Yes
No
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics
Connector End View Reference: Lighting Systems Connector End Views or Body Control System Connector End Views in Body Control System.
1
Did you perform the Lighting System Diagnostic System Check?
YES - Go to Step 2
NO - Go to Diagnostic System Check - Lighting Systems
2
Place the headlamp switch in the ON position.
Change the dimmer switch position from the high to low beam positions several times.
YES - Does the headlamp system operate normally?
NO - Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
Go to Step 3
3
Are both high and low beam headlamps inoperative?
YES - Go to Step 4
NO - Refer to Headlamps Inoperative - Low Beams or Headlamps Inoperative - High Beams
4
With a scan tool, observe the headlamp switch parameter.
Does the scan tool indicate ACTIVE? YES - Go to Step 7
NO - Go to Step 5
5
Connect a test lamp between the ground circuit of the headlamp switch connector and battery positive voltage.
Does the test lamp illuminate?
YES - Go to Step 6
NO - Go to Step 9
6
Test the headlamps switch headlamps on signal circuit of the headlamp switch for a high resistance, an open, or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 12
Go to Step 8
7
Inspect for poor connections to the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 12
Go to Step 10
8
Inspect for poor connections to the headlamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 12
Go to Step 11
9
Repair the ground circuit of the headlamp switch.
Did you complete the repair?
Go to Step 12
--
10
Important: Perform the setup procedure for the body control module.
Replace the body control module. Refer to Body Control Module Replacement
Did you complete the replacement?
Go to Step 12
--
11
Replace the headlamp switch. Refer to Headlamp Switch Replacement
Did you complete the replacement?
Go to Step 12
--
12
Operate the system in order to verify the repair.
Did you correct the condition?
System OK
Go to Step 3
SOURCE: 99 gmc denali dash light, parking lights, tail
You have a short to ground somewhere in the drl-fog lamp circuit. Check for obvious wiring connector or wiring to drl & fog lamps. check wiring for pinched or broken wires coming from sockets. If you don't find problem, you can trace wiring from lamps to main harnesses and hopefully find source of short.
hope this helps.
SOURCE: daytime running lights work but go out when I turn
If you have daytime running lights but when you turn on your regular headlight on they do not come on. Take the bottom of your steering column off (Two Small Screws) and look at the back of your turn/dimmer switch make sure that the light blue wire is connected. The wires will break off after years of raising and lowering your steering column.
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