DRL (Now fog lights too) always on

[brtaus]

Originally Posted by thebrainhart

Yes, I did, with my dirty fingers, you could see the fingerprint perfectly, so I thought about it, and blotted them out

That's funny because I know why you did that, and I think about that same reason when people post their license plate on here.

[Toasty]

yeah i dont think the switch is actually switching voltage, only a signal back to the BCM... think of it as a selectable relay of sorts...

[IROCanSS]

ATTENTION....

Anyone doing this method... you are constantly backfeeding your PCM when you have the fogs (DRLs) jumped off the parking lamps as described.

Here is a reply I got that made me look into it:

one thing from what I have looked into is that the placement of the diode, I talked with the master tech from the dealership and going over the wiring. If there is a power surge, when the cars PCM thinks the fogs should be off it could possibly cause a back feed and cause problems. If that does happen the dealer has every right to void the warranty on the PCM and all the entire electrical system....

I rewired with diodes to prevent the back feed to the PCM when the fogs are feeding off the parking lamps. That was a HUGE oversite. Those diodes need to be installed. Follow my attached diagram using 4 diodes. Even of you don't do a switch, you need to prevent this backfeed. If you follow the current, you will see that without the inline diodes on the dark blue and light blue, current can flow free back to the PCM.

Basically on "thebrainhart" method, whenever you have the headlights on, the PCM is getting backfed... BAD!!!

I am not saying his method is wrong, it works great and he did us a great service by figuring this out, i jsut wanted to let everyone know about this. I am betting the "plug and play" jumpers are causing this too!

WRONG WAY:



RIGHT WAY:

[thebrainhart]

Originally Posted by jrhaus76

ATTENTION....

Anyone doing this method... you are constantly backfeeding your PCM when you have the fogs (DRLs) jumped off the parking lamps as described.

Here is a reply I got that made me look into it:



I rewired with diodes to prevent the back feed to the PCM when the fogs are feeding off the parking lamps. That was a HUGE oversite. Those diodes need to be installed. Follow my attached diagram using 4 diodes. Even of you don't do a switch, you need to prevent this backfeed. If you follow the current, you will see that without the inline diodes on the dark blue and light blue, current can flow free back to the PCM.

Basically on "thebrainhart" method, whenever you have the headlights on, the PCM is getting backfed... BAD!!!

I am not saying his method is wrong, it works great and he did us a great service by figuring this out, i jsut wanted to let everyone know about this. I am betting the "plug and play" jumpers are causing this too!

Yes it is true it is backfeeding the line. It does not go to the PCM, but rather the fuse block/junction block/power module (whatever GM calls it).

If the fuse block required an empty circuit from the fogs (when off), and we were feeding it, then yes there would be a problem there. In this case, the fuse block is not telling the fogs to be off, but rather its not telling the fogs to be on, so it does not require an empty line.

Can doing this void your warranty? Yes, just like everything else on this website.

Is it going to damage your electrical system in your car if wired as originally described? It is possible, but it is a very, very insignificant chance.

I also am a "master tech" and I've never seen any problems with feeding an empty circuit with power, unless like I said it needs to be empty.

I've done similar things to all my vehicles. I did a very similar thing to my 08 Silverado, over 2 years and 25,000 miles ago, with zero problems.

I've had this on my Camaro for over 5 months and over 3,000 miles with no problem.


That being said, it is your car, if you want to take extra steps, it doesn't hurt. The diodes are cheap enough, and you are already there.


But my car will stay like this, and I'll never have any problems with it.

[Treefrog]

Done this mod... No issues and no regrets.. Luv it!

[Luttinger]

I had one silly question. Is that diode thing realy necessary?
So far (Afterburner, etc.) I connecting cables without using diodes.
Or is this something else?

Sorry if it was already explained and I haven't read it.

And how can I wire that the halo-rings are on with the DRL, but the DRL (fog lights) turn off when the HID turned on?
Would there be a way to wire this?

[thebrainhart]

Originally Posted by Luttinger

I had one silly question. Is that diode thing realy necessary?
So far (Afterburner, etc.) I connecting cables without using diodes.
Or is this something else?

Sorry if it was already explained and I haven't read it.

And how can I wire that the halo-rings are on with the DRL, but the DRL (fog lights) turn off when the HID turned on?
Would there be a way to wire this?

Without the diodes, the DRL circuits would power on the front side marker lights, and probably (depending on how everything is wired up) would power on all park lights, basically back feeding things that shouldn't be back fed. Basically what jrhaus76 was talking about above.

Not using the diodes in this case would be a bad thing, and probably would cause problems. In this thread, some people have wired up and have damaged the diodes and such, and they had some funky electrical problems.

To do the halo with DRL wiring, you'd have to figure out what wires are the halo's, then you could do a similar job like this one to make the halo's be on whenever they are requested on, and whenever the DRLs are on.

I've promised people that I'd look into this, but I havent yet, sorry guys

[Luttinger]

Thanks for the quick and satisfying explanation.

My front side markers switched as turn signal. It has to be wired that way within Germany.

I guess I will wait then until you have some instructions on the DRL mode Halo-Rings with fog-lights, because my favourite one is indeed that the fog-lights and halo-rings run on DRL mode, and fog-lights switch off when HID is running. Hope to read from you soon.

[augustst8607]

used the diagram from strauchpete this weekend. ran one 5 conductor 18 gauge cbl inside the car. wired 2 switches 1 for the drl's with p13 led's and 1 for the fog halos. works like a charm. drl's are functional as factory but now can be turned on with any lights on as well as the foglight halo's....thanks again strauchpete for the quick answers.

[strauchpete]

Originally Posted by augustst8607

used the diagram from strauchpete this weekend. ran one 5 conductor 18 gauge cbl inside the car. wired 2 switches 1 for the drl's with p13 led's and 1 for the fog halos. works like a charm. drl's are functional as factory but now can be turned on with any lights on as well as the foglight halo's....thanks again strauchpete for the quick answers.

Np man glad that I could of been some help.

From doing more research into it and talking with some more tech on the chevy tech forum, and looking into the backfeeding issue of the cars computer.

The fog lights go into the under hood fuse block, from there they go into BCM the BCM circuit goes out to the switch, from the switch to the PCM, from the pcm to the ing harness, from the harness to the battery.

So how this works factory,
Auto mode - the photodiode on the dash, when it is energized by light it tells the pcm that it is sunny out so to turn off the head lights and turn on the drls.
As the sun goes down less light hits the diode and it sends the signal to the computer telling it that its dark out and to turn off the drls and to the head lamps.

As the switch goes just works like the photodiode but you physically turn on and off the signal to the pcm to the bcm to the lamps.

So when you do the rewire and do not worry about the back feed or isolation from the circuits you are pretty much making the DRLs and the running lamps the same circuit and in the computer they are separate.

The problem from what the techs on the forum said is that the computer goes over pids all the time to make sure that everything is ok with the car, and the back feeding into the BCM and PCM eventually the car will think there is something wrong and it will not put up a check engine light because it is not a system that will throw a code but it will store one in the memory.

The other problem is that what most of techs said is the biggest problem is that by the rewire there is no fusing to protect the computer, so if there is a DRL that goes out it can send a short or a voltage spike back into the PCM and BCM that is all low current and can short out because also the running lamps are only a 10a circuit and the DRLs are a 15a circuit so you will be powering the running lamps, DRLs, and halos off of a circuit that is 5 amps less when it needs to be 10 amps more.

I mean these ways will all work but personally speaking my $25000+ cars are worth the extra $5 for either 2 extra diodes or relays, you can never be to save when it comes to doing extra addons.


Also I am making a plug and play harness with relay that I hopefully will have ready next week.
What it will be is like the other harness that are being sold but it will not use diodes it will use a relay, so what will it need is unplug the drl plug in this harness and then run one wire up to the battery and one to a ground. Then I will be a doing another one that will have a switch add on to it also.

[mmongi7]

Good info for the halos. Might have to try this out.

[FwyFlyer]

Originally Posted by thebrainhart

Glad to see its easy without removing the bumper. I wasnt sure there would be enough comfortable room to solder, going in that way.

I'm going to change the instructions mentioning it.

Thanks to everyone on this thread. I made my own harness(s) for this mod. My final version includes a relay and no diodes. I just need to wire in a switch for full control. I really don't want to drill a hole in the cabin to mount it so I'm putting it off for now. I'll get pics of the lights when I can pull it out of the garage.
Pics of my harnesses and relay:

Harness coupled to the bumper harness:

Wheel well shot of the install:

Relay mounted to the left of the fuse block:

[R1CH]

Originally Posted by FwyFlyer

Thanks to everyone on this thread. I made my own harness(s) for this mod. My final version includes a relay and no diodes. I just need to wire in a switch for full control. I really don't want to drill a hole in the cabin to mount it so I'm putting it off for now. I'll get pics of the lights when I can pull it out of the garage.

Can't you just wire up your harness to a constant hot, like the ignition, with an in line fuse for protection?

[FwyFlyer]

Originally Posted by R1CH

Can't you just wire up your harness to a constant hot, like the ignition, with an in line fuse for protection?

The front side markers trigger the relay when they come on. I just want to be able to turn them off if I want. Not really an issue because the LED DRL/fogs look real nice . Now if it would only stop snowing here so I could take it out of the garage!