Disable Auto-Headlights

[DEVILDOG]

I was wondering if anyone knows a way to permanently disable the auto-headlight function. I know that you can overide with the dome light switch but I want to always, manually, switch on the parking and headlights

My state requires two inspection stickers that are located in the bottom/center of the windshield and they always cast a shadow over the sensor. My headlights come on even when it is not very "dim" outside.

Thanks.

 

[Capecruis8der]

DevilD
when you overide the auto feature
you can turn your lights on separately by the switch
or should I say, at least I can

 

[DEVILDOG]

Thanks, but I want it to be overide all the time. Just picky I guess.

Whenever the vehicle is turned off it clears the overide function for the headlights.

 

[ShapeShifter]

I was wondering if anyone knows a way to permanently disable the auto-headlight function. ?I know that you can overide with the dome light switch but...

One way to do it is here.

-- SS

 

[JabotheHutt]

That was one of the options I didn't know I was getting until after I got home and played with the lights after dark. Kind of nice, these auto headlamps are, I would like to keep the DRL's lit without having to buy a kit, just for appearance.

I was wondering who had the devildog name on this BB. not often you run into another one.

Semper Fi Devildog! Alive or Dead, still a Marine!

 

[dmacker]

One way to do it is here.

-- SS

There has to be a less expensive way to kill the auto headlight. On a couple year older chevy I just took out one of the fuses. I can't remember which one, but it should be in the wiring diagram.

 

[AVid]

Ok wiring gurus...I too want to disable my auto headlamps. I know about the overide feature but that is a pain also. Here's my question, Is there a way to "fool" the sensors into thinking it is daylight out all the time? I am assuming that the sensors are nothing more than switches whose wiring either go to the BCM or to a junction box somewhere. Would it be a simple matter of unplugging the sensor or jumping a wire somewhere? I need someone with a wiring diagram to see where the wires from the sensors go. I don't want to take off the top pad to get to the sensors, I am interested where the other end of the wires go. Thanks in advance for any help.

 

[ShapeShifter]

Here's my question, Is there a way to "fool" the sensors into thinking it is daylight out all the time?

First, the requisite discliamer: All of the following information is obtained by reading the factory service manual. It is correct to the best of my knowledge, but I have not indiependantly verified any of this information, and I have not tried this modification myself. Anytime you go cutting and splicing wires, you run the risk of causing electrical damage to your truck, especially when dealing with inputs to a costly and sensitive item like the Body Control Module (BCM) which is in essance a specialized control computer. Using this information, and performing modifications to your truck, is entirely at your own risk. I will help as much as I can from the far end of a computer keyboard, but if you melt wires or burn up a BCM, I'm not responsible, and I'm not paying for repairs!


Please take note, the following discussion applies only to 2002 models. 2003 is different, and I don't have that information.

OK. with that out of the way, I did a little research. According to the wiring diagrams, the ambient light sensor is a photodiode. It has two wires, both of which run directly to two pins on the BCM, using the purple connector C3:

​

Pin A4 (highlighted in red) is a 5 volt reference output, and is a grey wire.

Pin A6 (highlighted in green) is the ambient light sensor signal, and is a white wire.

The ambient light sensor signal voltage varies according to the amount of light on the sensor. It is considered to be light if the voltage is between 2.2 and 4.7 volts, and dark if between 0.2 and 1.3 volts. (There is a dead band between the two ranges to prevent the lights from constantly swtiching on and off at twilight.)

There are a variety of diagnostic scan codes that get logged if the reference voltage is out of range, and probably also if the sensor voltage is out of range. In the documentation for the scan codes, it states that the DRLs will be inoperative if the scan codes are set. As I wouldn't think this is important enough to light the service engine warning, this may be how they alert the driver to a problem. (Owner to service manager: "Hey, somethings wrong, my DRLs don't work!")

Simply unplugging the sensor will result in 0 volts on the input, so the BCM should not only think it is dark, it will probably log a scan code and disable the DRLs.

Jumping the 5 volt reference directly to the ambient light sensor input should make the BCM think that it's light, but will also probably log a scan code and disable the DRLs. But then again, it's so simple, maybe it's worth a try. Don't cut the wires, just use a ScotchLock crimp on splice connector to short them together? I don't know, it might or might not work.

Probably the best bet is to clip the reference and sensor wires near the BCM, and connect a resistor across them. The value of the resistor would need to be determined by experimentation. Connect a volt meter between the sensor input and ground, and then try various resistor values (or use a variable resistor) until the sensor input voltage is around 3 to 4 volts. Then make sure everything is secure and insulated.

Doing this, the BCM would always think that it's daylight, and should never go into auto mode.

To take this one step further, a switch could be added that would switch the BCM input between the sensor and the resistor. Throw the switch one way, and the sensor is connected and the resistor is open, and you have auto mode. Throw it the other way, the resistor is connected, the sensor is open, and you are in manual bypass mode.

The service manual indicates a couple of warnings about working with the BCM. Always disconnect the negative terminal of the battery first. Also, if you are going to unplug any of the BCM connectors, always unplug the brown connector first. When reconnecting things, always plug in the brown connector last.

One last detail. To get to the BCM, remove the plastic knee bolster panel below the steering wheel. Behind it you will find the BCM, which is a box with a row of three large connectors: brown, lght blue. and purple.

I hope this helps. If you decide to try this, let us know how it turns out, and especially what resistor value you used.

Good luck, Mr Phelps...

-- SS

 

[pdxkevin]

Mine doesn't automaticlly revert back to the automatic setting. It stays at manual until I switch it back on. Its worth a try.

If we all turn our '02 owners manuals to 2-55 under the section heading of Daytime Running Lamps. ?(I didn't find this on my own, either. ?It was shown to me by one of the Av club gurus).

There is the procedure for turning off the automatic headlamp system.

When necessary, you may turn off the aitomatic headlamp system and the DRL feature by the following steps:

• Turn the ignition to RUN.
• Press the DOME OVERRIDE button four times within six seconds. After the fourth press of the button, a chome will sound informing you the system is off. The system will revert back to the automatic mode when the ignition is turned odd and on again.
• to return the automatic mode, push the DOM OVERRIDE button four times within six seconds (the chime will sound), or turn the ignition off and on again.

They say this only applies to AVs sold in the US.

 

[AVid]

Many thanks for your research SS. It turns out this is more involved than I thought it would be. Maybe it would be easier to tape a flashlight on the dash pad!! If I can work up the courage, I'll give it a try and post the results. Thanks again.

 

[ShapeShifter]

Mine doesn't automaticlly revert back to the automatic setting. It stays at manual until I switch it back on. ?Its worth a try.

On my 2002, this does work. However, as soon as I turn off the truck, the next time I go to start it, it's back in auto. On second thought, let me verify that...

Time passes...

OK, I'm back. At least on mine, the manual override does indeed reset back to auto after shutting off the ignition.

Just to be complete, here is the portion of the 2002 wiring diagram as it applies to the sensor:

​

There really isn't much to it.

Also visible here is the output going to the headlight relay. The BCM puts out voltage on this output in order to turn on the headlight relay, which in turn powers up the headlights. At first thought, it would seem like snipping this wire could deactivate the auto headlights, and it does, to a degree. When the sensor sees dark, snipping that wire will keep the headlights off, but the DRLs will still turn off, and the parking/tail lights will still come on. Therefore, all this will do is prevent the headlights from coming on automatically, but it will not dactivate the auto function.

Substituting a resistor for the sensor, and even adding a switch, should not be a difficult thing for the confident modder to attempt. It is not, however, a simple plug-and-play mod. A little bit of investigation and experimentation must be done by a brave soul before the timid should try to do it. (got_change, AutoWorker, XRover, Jackalanche, and the other bold pioneers: are you listening?)

Remember, all this only applies to 2002. 2003 is different.

-- SS

 

[ShapeShifter]

Kevin, I just took another look at your post. The key is right there at the end of your quote from the manual:

to return the automatic mode, push the DOM OVERRIDE button four times within six seconds (the chime will sound), or turn the ignition off and on again.

Right there, it says turning off the ignition will reset it. That means someone like DEVILDOG with inspection stickers over the sensors must override the lights every time they start the truck.

So, in my mind, while I really don't have a personal need for a "permanent" manual override, I can see where others may need it.

Also, I think that using the override, also disables the DRLs. That means that not only will someone like DEVILDOG have to hit the override every time, but he will also lose the DRLs when he does so.

They say this only applies to AVs sold in the US.

That's becuase in the US, DRLs are an optional safety feature. In Canada (our owner's manuals are written for both countries) they are required on all vehicles that are sold for the first time in Canada. The Canadian regulations say that you must not be able to turn off the DRLs, they must be on at all times (except when the headlights are on.) Since the headlight and DRL overrides are one and the same, I guess you lose both functions in Canads.

-- SS

 

[AVid]

I guess I should have explained my reason for wanting this mod. My headlights will stay on even on a cloudy day at high noon. If I overide the auto it shuts off all exterior lighting, that includes the DRL's. If this was going to be easy I could save myself a trip to the dealer to check on the sensors. Although I have a great dealer, it is still a pain to be without a AV for a day. Thanks again. Merry Christmas to all.

 

[Capecruis8der]

If you you do the DRL, always on mod,
when you diable the auto lites, the DRL's will stay on
then, it might be easier to put a switch on the DRL's if you didn't want them on

AV a nice day

 

[AVid]

OK ShapeShifter....Would this be a fair assumption. If I find a way to apply 2.2 to 4.7 volts to pin A6 in BCM's C3 plug, it should fool the BCM into thinking it was daylight all the time.

Capecruis8der....I understand what your saying, but I don't want to have to push the button every time I start the truck. This has nothing to do with my DRL's, just my headlights being on even on a cloudy day. It has to be fairly bright outside before my headlights go off.

Thanks again group.

 

[ShapeShifter]

OK ShapeShifter....Would this be a fair assumption. If I find a way to apply 2.2 to 4.7 volts to pin A6 in BCM's C3 plug, it should fool the BCM into thinking it was daylight all the time.

Yep, that's my take on it as far as 2002 models go.

-- SS

 

[Bobbll]

First, the requisite discliamer: All of the following information is obtained by reading the factory service manual. It is correct to the best of my knowledge, but I have not indiependantly verified any of this information, and I have not tried this modification myself. Anytime you go cutting and splicing wires, you run the risk of causing electrical damage to your truck, especially when dealing with inputs to a costly and sensitive item like the Body Control Module (BCM) which is in essance a specialized control computer. Using this information, and performing modifications to your truck, is entirely at your own risk. I will help as much as I can from the far end of a computer keyboard, but if you melt wires or burn up a BCM, I'm not responsible, and I'm not paying for repairs!


OK. with that out of the way, I did a little research. According to the wiring diagrams, the ambient light sensor is a photodiode. It has two wires, both of which run directly to two pins on the BCM, using the purple connector C3:

​

Pin A4 (highlighted in red) is a 5 volt reference output, and is a grey wire.

Pin A6 (highlighted in green) is the ambient light sensor signal, and is a white wire.

The ambient light sensor signal voltage varies according to the amount of light on the sensor. It is considered to be light if the voltage is between 2.2 and 4.7 volts, and dark if between 0.2 and 1.3 volts. (There is a dead band between the two ranges to prevent the lights from constantly swtiching on and off at twilight.)

There are a variety of diagnostic scan codes that get logged if the reference voltage is out of range, and probably also if the sensor voltage is out of range. In the documentation for the scan codes, it states that the DRLs will be inoperative if the scan codes are set. As I wouldn't think this is important enough to light the service engine warning, this may be how they alert the driver to a problem. (Owner to service manager: "Hey, somethings wrong, my DRLs don't work!")

Simply unplugging the sensor will result in 0 volts on the input, so the BCM should not only think it is dark, it will probably log a scan code and disable the DRLs.

Jumping the 5 volt reference directly to the ambient light sensor input should make the BCM think that it's light, but will also probably log a scan code and disable the DRLs. But then again, it's so simple, maybe it's worth a try. Don't cut the wires, just use a ScotchLock crimp on splice connector to short them together? I don't know, it might or might not work.

Probably the best bet is to clip the reference and sensor wires near the BCM, and connect a resistor across them. The value of the resistor would need to be determined by experimentation. Connect a volt meter between the sensor input and ground, and then try various resistor values (or use a variable resistor) until the sensor input voltage is around 3 to 4 volts. Then make sure everything is secure and insulated.

Doing this, the BCM would always think that it's daylight, and should never go into auto mode.

To take this one step further, a switch could be added that would switch the BCM input between the sensor and the resistor. Throw the switch one way, and the sensor is connected and the resistor is open, and you have auto mode. Throw it the other way, the resistor is connected, the sensor is open, and you are in manual bypass mode.

The service manual indicates a couple of warnings about working with the BCM. Always disconnect the negative terminal of the battery first. Also, if you are going to unplug any of the BCM connectors, always unplug the brown connector first. When reconnecting things, always plug in the brown connector last.

One last detail. To get to the BCM, remove the plastic knee bolster panel below the steering wheel. Behind it you will find the BCM, which is a box with a row of three large connectors: brown, lght blue. and purple.

I hope this helps. If you decide to try this, let us know how it turns out, and especially what resistor value you used.

Good luck, Mr Phelps...

-- SS

Simply remove the ambient light sensor wires from the connector and plug in a 680 ohm resistor. I've done it on a 01 Silverado and an 02 Trailblazer that I owned.

Works great. Gives you a completely functional headlight switch without pushing that stupid button 4 times.

Why is it that GM doesn't give me credit for knowing when to turn on my headlights?

 

[ShapeShifter]

Simply remove the ambient light sensor wires from the connector and plug in a 680 ohm resistor. ?I've done it on a 01 Silverado and an 02 Trailblazer that I owned.

Welcome to the club, Bobbll!

Sounds like someone's done the experimenting and come up with the right resistor value: 680 ohms.

Is there a connector on the light sensor? That sounds like it would be a good place to make the connection. There is a trade-off involved: making the cut/splice at the BCM is simpler in that the whole top of the dash does not need to be removed. However, making the substitution at the sensor is safer, in that it may not be necessary to cut any wires. Can the resistor simply plug into the connector on the wire?

Thanks for posting! It's always great to come up with additional ways to do things.

Why is it that GM doesn't give me credit for knowing when to turn on my headlights?

I like the auto lights a lot. I had the auto lights in my old Blazer, and as far as I know, there was no override. At least the '02 models have the override, even though it could be more convenient.

I think the '03 is the best: if I recall correctly, the headlight switch has a fourth position: off, auto, park, headlights. That's the best way to do it. You can choose auto or fully manual modes. And if you choose manual, it doesn't reset everytime you turn off the ignition!

-- SS

 

[TXAVy]

I agree, I like the '03 switch as well except for two things.

1) The "press the dome light button 4 times" override trick doesn't work, though with an "off" position I guess it doesn't need to.

2) There is a "feature/quirk" about the '03 lights that I can't currently find a way around.

• Start your truck.
• Press the brake and take the truck out of park so the DRLs come on.
• Turn your headlight switch to "Park" so your parking lights come on.
• Here's the tricky part, if you have an '02 truck, you will now have your Parking lights and your DRLs (hopefully amber) on. If you have an '03 though, the DRLs go OFF as soon as the parking lights come on. Hey! I WANTED them both on!!!

Anyone know a way on the '03 to run with both Parking lights and DRLs on at the same time aside from running into mods

 

[ShapeShifter]

1) The "press the dome light button 4 times" override trick doesn't work, though with an "off" position I guess it doesn't need to.

I agree. WIth the "off" position, there's no need for a "secret" override method.

[*]Here's the tricky part, if you have an '02 truck, you will now have your Parking lights and your DRLs (hopefully amber) on. If you have an '03 though, the DRLs go OFF as soon as the parking lights come on. ? Hey! I WANTED them both on

Well I'll be! I was just about to write that the '02 DRLs turn off as soon as you turn on the parking lights. But before I did, I just went out to see. I had to pull the truck out of the garage, AND shine an 18V flashlight on the sensor to get the auto lights to turn off. (It's gloomy and snowing right now, and if I used the dome light override operation, it would also turn off the DRLs.)

I finally got the auto lights off, turned on the park lights, and lo and behold, they were both on.

Cool, I learn something new every day. I thought all of the "4 amber" pictures were done with the full-time DRL mod.

As for you and your "4 amber" desires, I'll take a guess that you need the full time DRL mod.

-- SS

 

[TXAVy]

As for you and your "4 amber" desires, I'll take a guess that you need the full time DRL mod.

Yeah, that's what I'm worried about. And now that I've got Amber DRLs, they don't look so good with the Fog lights. So now I'm pondering whether I should get a set of amber fog lamps, or get brighter DRL/Fog lamps and just go back to white on both.

 

[Bobbll]

Welcome to the club, Bobbll!

Sounds like someone's done the experimenting and come up with the right resistor value: 680 ohms.

Is there a connector on the light sensor? That sounds like it would be a good place to make the connection. There is a trade-off involved: making the cut/splice at the BCM is simpler in that the whole top of the dash does not need to be removed. However, making the substitution at the sensor is safer, in that it may not be necessary to cut any wires. Can the resistor simply plug into the connector on the wire?

Thanks for posting! It's always great to come up with additional ways to do things.

I like the auto lights a lot. I had the auto lights in my old Blazer, and as far as I know, there was no override. At least the '02 models have the override, even though it could be more convenient.

I think the '03 is the best: if I recall correctly, the headlight switch has a fourth position: off, auto, park, headlights. That's the best way to do it. You can choose auto or fully manual modes. And if you choose manual, it doesn't reset everytime you turn off the ignition!

-- SS

I didn't look at the sensor to see if there was a connector there - too much work to get to that.

Once I found the sensor wires at the BCM connector, I went to Pep Boys and bought the tool to remove the pins from the BCM plug. Plugged in a 1K pot and tweaked until I found the same voltage drop that full daylight gave me across the ambient light sensor. Unplugged the pot and measured approx. 680 ohms.

Went back to Pep Boys and bought "GM ECM" pins and soldered to 680 ohm 1/4 watt resistor. Tied back the light sensor wires and inserted resisitor pins into BCM plug.

The beauty of this is that NO wires were cut or spliced and the mod can be completely undone by removing the resistor and plugging the wires back into the BCM plug. I think the pin removal tool cost a whopping $7.00.

BTW, after the 01 Silverado and 02 Trailblazer, I now have the 03 Av. Absolutely the best of my last two, but with NO compromises.

Alas the 03 has a spring loaded 4th position on the headlight switch. Turn it to the left past Auto and release it. Now its in manual mode for that ignition cycle. Much better than pushing a button 4 times. It looks like I won't need to do the mod on my 03 though.

Outstanding site here. Retired Jarhead from Jax, FL happy to be on board.

 

[ShapeShifter]

So now I'm pondering whether I should get a set of amber fog lamps,

I won't make a decision for you, but if you somehow do find amber halogen fog lamp bulbs, make sure you post that information on thiis topic here.

There are a bunch of people on that topic that are looking for the holy grail of amber halogen bulbs. So far as I know, nobody has found any yet.

-- SS

 

[ShapeShifter]

Once I found the sensor wires at the BCM connector, I went to Pep Boys and bought the tool to remove the pins from the BCM plug. ?Plugged in a 1K pot and tweaked until I found the same voltage drop that full daylight gave me across the ambient light sensor. ?Unplugged the pot and measured approx. 680 ohms.

Went back to Pep Boys and bought "GM ECM" pins and soldered to 680 ohm 1/4 watt resistor. ?Tied back the light sensor wires and inserted resisitor pins into BCM plug.

The beauty of this is that NO wires were cut or spliced and the mod can be completely undone by removing the resistor and plugging the wires back into the BCM plug. ?I think the pin removal tool cost a whopping $7.00.

Well, there you have it folks, the definitive answer to to this question. This sounds like the best way to do this.

Good job, bobbll!

Alas the 03 has a spring loaded 4th position on the headlight switch. ?Turn it to the left past Auto and release it. ?Now its in manual mode for that ignition cycle. ?Much better than pushing a button 4 times. ?It looks like I won't need to do the mod on my 03 though.

I didn't know that the manual position was spring loaded!

You have to hit it every time if you always want manual control? That's not much of an improvement over the "push four times" method, other than you don't have to try to remember the "secret handshake."

It could've been done so much better...

-- SS

 

[darkwingZ24]

Well here in Canada GM for some reason didn't program the functionality of the 'off' posittion... something to do with the law requiring DRL's, but what's annoying is that I cannot turn off my headlights at all inthe dark. All vehicles I've driven if the vehicle is in park and e-brake is on the lights turn off. But in 2003 GM vehicles no longer do this. Really bad if you want to turn your truck on at the drive-in

I will be trying this mod ASAP! I can understand not letting you turn off the lights while driving, but honetly if the vehicle is PARKED and E-BRAKE is ON... what gives?