On my 2005 T'blazer, the automatic headlights no longer turn off when locks and alarm is set in auto mode. I remove the #46 relay in the under hood fuse box and the headlights go off but the parking lights stay on with the switch in auto. Put the relay back in and the headlights come right back on when they shouldn't be on. The only way to turn them off is by turning the headlight switch full off to the left to the spring loaded off position and release it. Then the headlights will go out. I've read that there is some kind of module under the dash that might have failed, or maybe it's the switch? If it's the module does anyone have a name ad part number and where it's located? Thanks!
NEED HELP Headlights won't turn off in auto mode when doors are locked with fob
- Thread starter 767Jockey
- Start date
I would say your headlamp switch is faulty.
The headlight switch grounds out signal wires from the BCM for each of the modes of headlamp/park lamp operation.
I would not think it is related to the DRL since that doesn't turn on the Park lamps.
Have you any sort of scantool?
The headlight switch grounds out signal wires from the BCM for each of the modes of headlamp/park lamp operation.
I would not think it is related to the DRL since that doesn't turn on the Park lamps.
Have you any sort of scantool?
I'm lost on all the acronyms- I'm not familiar with BCM, DRL, DIC. The car has got an automatic setting on the headlights where they go on when it gets dark enough. When you leave the car and lock it with the remote key fob, the car chirps and then the headlights normally stay on for a short period of time then they go off. It's not doing that now. The car chirps but the headlights never go off. They stay on until you use the headlight switch to manually turn them off. After turning them off, if you reposition the switch back to the automatic position, they come right back on and won't go off unless you manually turn them back off again. I only have a OBD2 tool, that's all I have.
BCM: Body Control Module
DRL: Daytime Running Lights
DIC: Driver Information Center
You previously said the Park Lamps also stay on. That would be a good clue to what is happening because they are a separate relay, not interconnected with the headlamps.
For BOTH the headlamps and the Park lamps to be affected suggests an issue with the switch. Or possibly a wiring fault between the switch and the BCM. Specifically the grey/black wire on terminal E of the headlamp switch. If that wire gets grounded the Park and Headlamps are turned on.
DRL: Daytime Running Lights
DIC: Driver Information Center
You previously said the Park Lamps also stay on. That would be a good clue to what is happening because they are a separate relay, not interconnected with the headlamps.
For BOTH the headlamps and the Park lamps to be affected suggests an issue with the switch. Or possibly a wiring fault between the switch and the BCM. Specifically the grey/black wire on terminal E of the headlamp switch. If that wire gets grounded the Park and Headlamps are turned on.
Eric "O" from South Main Auto (SMA) regales us with "The Universal Diagnostic Steps" to figure this problem out using a Loaded Test Lamp, a Lighted Pin Probe with a Red Power Jumper Wire and the GM OEM Wiring Diagram to Reverse Trace the Operation of the System (Works for Both the Envoys and Trailblazers) to include The High and Low Beam Lamps, The Circuit Wiring Layout, The Cabin Lamp Switch Operation, The Head Lamp Fusing ...and The Special (PWM) HDM Relay for The Low Beams that may be Suspect in this instance if the one presently installed is NOT the recommended OEM ACDelco Version if it has Burned Out:
The VOP (Video Original Poster) in this Video explains what he did to solve a problem with his Headlight Beams NOT Turning OFF due to that Special Relay Overheating and Failing:
Even though Eric "O" purchased a NAPA HDM Relay Part# AR-6100 ... If your Original One proves to be Faulty... Try to find THIS OEM Relay Part #15016745 as it IS your BEST Replacement Choice:
PS... It should be noted that the VOP (Video Original Poster) in this Last Video did NOT get to the bottom of the "Flickering* Head Lamps issue. The answer to THAT Riddle is that if you View THIS Diagram below...you can see that the Left Head Lamp, The Left Turn Signal and the Fuel Pump Relay ALL SHARE THE SAME ENGINE BLOCK GROUND AT G-107.
If the Ground Wires are either Cut, Corroded or Compromised...a serious increase in Amperage Draw will occur and thus... The increased Electrical Resistance will cause the Head lamps to "*Flicker* whenever the Left Turn Signal is being used and the DRLs or High Beam Head Lamps are Turned ON while the Fuel Pump Relay is activating the Fuel Pump Motor.
If the resistance is serious enough...the Loss of Current can TRIP THE FUEL PUMP RELAY OFF... and cause the Vehicle to STALL. Cleaning up the Ground Wire Tang and Engine Block Surfaces and using a Small Dab of Dielectric Grease should solve the Bad Ground issues from happening from then on.
The VOP (Video Original Poster) in this Video explains what he did to solve a problem with his Headlight Beams NOT Turning OFF due to that Special Relay Overheating and Failing:
Even though Eric "O" purchased a NAPA HDM Relay Part# AR-6100 ... If your Original One proves to be Faulty... Try to find THIS OEM Relay Part #15016745 as it IS your BEST Replacement Choice:
PS... It should be noted that the VOP (Video Original Poster) in this Last Video did NOT get to the bottom of the "Flickering* Head Lamps issue. The answer to THAT Riddle is that if you View THIS Diagram below...you can see that the Left Head Lamp, The Left Turn Signal and the Fuel Pump Relay ALL SHARE THE SAME ENGINE BLOCK GROUND AT G-107.
If the Ground Wires are either Cut, Corroded or Compromised...a serious increase in Amperage Draw will occur and thus... The increased Electrical Resistance will cause the Head lamps to "*Flicker* whenever the Left Turn Signal is being used and the DRLs or High Beam Head Lamps are Turned ON while the Fuel Pump Relay is activating the Fuel Pump Motor.
If the resistance is serious enough...the Loss of Current can TRIP THE FUEL PUMP RELAY OFF... and cause the Vehicle to STALL. Cleaning up the Ground Wire Tang and Engine Block Surfaces and using a Small Dab of Dielectric Grease should solve the Bad Ground issues from happening from then on.
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Mooseman
Moderator
Have you tried just leaving them on for a while to see if they eventually go out? It could be the perimeter lighting setting that automatically keeps the lights on for a set number of seconds. I think the longest is 60 seconds. And IIRC, there is also a battery preservation function that will turn off the lights after 10 minutes no matter where the switch is set.
Blckshdw
Moderator
That's what I was thinking too. There have been times where I've been working on something that required the headlights to be on, and they'd shut off after about 10 minutes (same with the radio under RAP mode)Did run out real quick to check the headlamp delay options, please don't mind my filthy cluster lens
Mine was the plain Jane LS model, with the DIC cluster added later. I don't remember what the default is set to, or if I ever changed this, but mine was set at 20 seconds FWIW. 
