2000-2002 Buick Century DRL & Automatic headlight removal

Thunderhawk09

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38
7
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Buick Ownership
2001 Buick Century Custom
2000-2002 Buick Century

Locate Body control Module (BCM). This unit is a black box approximately 6" square and 1-1/2" thick with 4 connectors entering one end. Hunting with the door open and key in the ignition, follow your ears to the chime inside. On the 2000-2002 Buick Century, it resides to the left of the steering column, right above your left foot. There is a bump in the fuzzy trim panel that covers the under dash area that gives clearance to the BCM wiring harness. The trim panel does not have to be removed completely to get in far enough to work. Pull out a couple of the panel retainers and work the left end down and back until you have working room. Those panel retaining fasteners are a push in "Christmas tree" type and can be difficult to remove. Persevere, this is the hardest part, The actual mods are easy.
The 4 connectors should now be visible almost even with the bottom of the dash. The connectors are color coded for identification. The first connector is C1, and is blue. We will be working with 4 out of the 7 wires in this connector. Locate the light blue, light blue w/white stripe, dark blue, and dark blue w/white stripe. The white striped wires are the front left and right feeds from the turn signal switch. The plain color wires go to the front left and right turn signal lamps. Very simply, cut all 4 wires about an inch from the connector and separately insulate the wires from the connector. Splice (and insulate) the like colors together that go into the harness. Dark blue to dark blue w/white, and light blue to light blue w/ white stripe. This removes the DRL function from the front turn signals.
The second connector is C2, and is purple. We will be working with only 2 of the 14 wires in this connector. Locate the yellow w/black stripe, and immediately adjacent to that, find the light green w/black stripe. These two wires connect to the Ambient Light Sensor. Cut these two wires about an inch from where they emerge from the harness. Connect a 4700 Ohm resistor (1/4 watt is fine) across the wires from the connector, and insulate. This makes the BCM stay in the daylight mode, and disables the automatic headlight function.
Test your work. Check operation of turn signals and headlights. Replace trim panel and congratulate yourself for a job well done.




Also have these fixes for other Buick and Gm Vehicles
 

ledzilla

Full Member
198
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2001 Century Custom
Call me a pain in the ass, but suppose you wanted this to be reversible in case you sold the car and they wanted the functions to work. Any thoughts on how instead of splicing you could wire in a switch to turn each function on and off?
 

Thunderhawk09

Member
38
7
8
Buick Ownership
2001 Buick Century Custom
Call me a pain in the ass, but suppose you wanted this to be reversible in case you sold the car and they wanted the functions to work. Any thoughts on how instead of splicing you could wire in a switch to turn each function on and off?
Please do not take this the wrong way when I say with 190k miles on car there is a good chance it wont make it too another owner and nothing I do like this is done that cant be reversed wires was left long enough on BCM to put back as well as the auto headlights and as long as I have the car I do not really Give a crap about a possible next owner I will cross that bridge when I get to it and switching not really a option since turn signals had to be completely cut loose from BCM to Eliminate them. Same for auto headlights they too had to be cut free and the 4700 Ohm resistor added between the two wires from the BCM to trick car into being in daytime mode all the time I could have gotten use to the auto headlights but the fact the E brake had to be set to keep them from turning on when trying to start car was BS. There was a better way GM could have done them buy have BCM sense when car had started with a tachometer wire to the BCM that would have given the full battery to the starter till BCM had a tachometer signal then the auto headlights could have came on and auto headlight should have had a programmable mode to set them to go off when put in Park because some like me does not like the delayed off either
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ledzilla

Full Member
198
14
18
Buick Ownership
2001 Century Custom
Here's two links on the DRL and one list's other GM models:
DADRL - How To Disable DRLs

This one has a switch as a option on a 04 along with a wiring diagram.
Buick Century: Where is the DRL (Daytime Running Light) module…
I've actually read the DADRL article and have it bookmarked. Found it last year I think, but never did anything.

Please do not take this the wrong way when I say with 190k miles on car there is a good chance it wont make it too another owner and nothing I do like this is done that cant be reversed wires was left long enough on BCM to put back as well as the auto headlights and as long as I have the car I do not really Give a crap about a possible next owner I will cross that bridge when I get to it and switching not really a option since turn signals had to be completely cut loose from BCM to Eliminate them. Same for auto headlights they too had to be cut free and the 4700 Ohm resistor added between the two wires from the BCM to trick car into being in daytime mode all the time I could have gotten use to the auto headlights but the fact the E brake had to be set to keep them from turning on when trying to start car was BS. There was a better way GM could have done them buy have BCM sense when car had started with a tachometer wire to the BCM that would have given the full battery to the starter till BCM had a tachometer signal then the auto headlights could have came on and auto headlight should have had a programmable mode to set them to go off when put in Park because some like me does not like the delayed off either
This thing has a lot of life left in it, especially given how much of the car has been rebuilt. And I don't intend to keep it too much longer, depending on how long it takes me to get some stuff resolved so I can build up a down payment for a TourX. Plus it's not my only car, so I don't have to rely on it as my only means of transportation. However, I did manage to come up with a concept that utilizes simple STSP switches and 5-pin relays which would allow for switching these functions on and off. It would take two switches and six relays. If I could find relays with one switching signal but two switches instead of one, only need three. Here's the concept:

For each pair of wires to be cut and rerouted, you need two relays. After making the cut in the wire, you wire the side away from the BCM to pin 30, and the side towards the BCM to pin 87. Do this for each pair of wires cut. In this fashion, the default function (DRL/auto lights) will only work when switched "ON". Then you wire pin 87a together between both relays (with the resistor in place for the auto lights) to make it the function with the switch "OFF". From there, you would just need to tap into a circuit that's powered with the key in the "RUN" position, and run that to the switch, and then to pin 85/86. I suppose you would want pin 85 for relays with an internal diode, otherwise it doesn't seem to matter as far as I can tell.

I actually already have the supplies on hand to do this, although my relay sockets use 12/14 ga wiring, so I may need to do some shopping. It's a mess trying to splice 18ga to 14ga and larger. Found that out when wiring in a new pigtail for the driver door window switch.
 

Thunderhawk09

Member
38
7
8
Buick Ownership
2001 Buick Century Custom
yeah I just did not want to switch mine and use two of the 6 spare relay's & harness's that I have for that when I knew I would never turn them back on
 

ledzilla

Full Member
198
14
18
Buick Ownership
2001 Century Custom
I'm the kind of variety that likes to turn things on and off and have cool looking switches to do it. And I tend to over-engineer solutions to things, even with my projects at work. Plus, I've been working a solution for using the white light from my switchback LED bulbs as DRLs instead of the amber, like it does normally. And I've been performing electrical repairs and upgrades on my old Fords. So, I already have switches, switch panel, relays, wiring, heat shrink, and whathaveyou, so I figure what the heck, why not go all out on this.

At any rate, the basic work required to disable the DRLs and automatic headlights looks simple enough. People just have to make sure they be careful when doing it so it stays in one piece, without any exposed wire that can accidentally ground itself.
 

Thunderhawk09

Member
38
7
8
Buick Ownership
2001 Buick Century Custom
To Add to what I have already done above I had discovered something else that I did not like about the way GM setup the high/low beam headlights some GM models the low beam stays on when high beams are active But not the century which caused a issue for me because I wanted to go hid but since the hid has a warm up period of about 10 seconds this made a hid conversion not safe since the headlights switch places there would be 10 second very low light output when switching to high and then back to lows so I installed a 10 amp diode between the low/high headlight so current could flow the one direction needed back to the lows when high's are active this not only add's better light when on high but since the lows now stay on when going to high it eliminates the 10 sec low light zone and provides the low lights while high beam builds its 10 sec warm up
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ledzilla

Full Member
198
14
18
Buick Ownership
2001 Century Custom
I had actually tried doing something similar to my old Town Car back in the day, messing around with the old sealed beam setup, but I was still new to automotive electrical and almost wrecked my headlights. Glad you got that working.
 
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