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2008 gmc envoy_sle
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Discussion Starter #1
Good Morning All, I have an issue I am hoping to get some assistance with.

I bought my Envoy 10 months ago, second hand. It's been a 1 previous owner. I don't really have any issues with it with the exception of the rear gate lifts are out on it and it didn't come with the space tire tool, so I have to get those fixed, but any case. Good Car! I love it.

A little over a month ago, I go out to use my car at dusk and the low-lamps won't come on. I'm confused, so I flip them to manual on the headlight switch (or DRL off) and nothin! I flip the high-lamp brights on, and they're fine. Back to Manual, nothin'. I get up the next morning and voila, the standard DRL low-lamp mode works, and so does manual! Off and on they would work and not work, intermittently at night. Sometimes they would work in the evening (rarely) and then flip off for a second and back on in the middle of me driving.

I discovered I could run the fog lamps for mild low light conditions to give me a little illumination, but needless to say. Dangerous!

I checked the standard fuses for each lowlamp, and then yesterday I went to O'Reilly's and there was a helpful guy who tried a new relay for the HDM module for me. Nothin. I'm at my wits end here, I've tried new relays, the fuses are good, the headlights are good. Can I try anything else?

In summary, no other electrical issues. The lowlamps are the only issue I have. They haven't come on at all in about a week - so whatever was allowing them to come on intermittently is now fried, I'd guess.

Thanks for the help!
 

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2008 gmc envoy_sle
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9 Posts
Discussion Starter #3
As I mentioned, I went to O'Reilly's last night and tested out a new relay switch, brand new. That didn't help. Headlights didn't work and there was no click or anything. So I don't think its the HDM relay.
 

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2004 trailblazer_lt
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5,240 Posts
As I mentioned, I went to O'Reilly's last night and tested out a new relay switch, brand new. That didn't help. Headlights didn't work and there was no click or anything. So I don't think its the HDM relay.
It may not be a relay, but if you do a search under "headlight relay" you will find information on further troubleshooting this problem. Good luck!
 

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2008 gmc envoy_sle
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9 Posts
Discussion Starter #5
Thanks for the pointers, I will continue to do so. This forum is kind of my last shot. I have spent the last 2 weeks searching online for ideas. I'm hoping to get some more direct feedback from people who have experience with Envoys!
 

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2004 trailblazer_lt
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5,240 Posts
Thanks for the pointers, I will continue to do so. This forum is kind of my last shot. I have spent the last 2 weeks searching online for ideas. I'm hoping to get some more direct feedback from people who have experience with Envoys!
Welcome to Trailvoy! You'll find information on just about anything here. Not sure, but you may have to have ten (10) post before you can access the search option, I can't [email protected]#, but Roadie can answer any electrical questions if a search doesn't turn up an answer. He our in-house electrical engineer guru! Have fun!:tiphat
 

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2009 chevy
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263 Posts
Good Morning All, I have an issue I am hoping to get some assistance with.

I bought my Envoy 10 months ago, second hand. It's been a 1 previous owner. I don't really have any issues with it with the exception of the rear gate lifts are out on it and it didn't come with the space tire tool, so I have to get those fixed, but any case. Good Car! I love it.

A little over a month ago, I go out to use my car at dusk and the low-lamps won't come on. I'm confused, so I flip them to manual on the headlight switch (or DRL off) and nothin! I flip the high-lamp brights on, and they're fine. Back to Manual, nothin'. I get up the next morning and voila, the standard DRL low-lamp mode works, and so does manual! Off and on they would work and not work, intermittently at night. Sometimes they would work in the evening (rarely) and then flip off for a second and back on in the middle of me driving.

I discovered I could run the fog lamps for mild low light conditions to give me a little illumination, but needless to say. Dangerous!

I checked the standard fuses for each lowlamp, and then yesterday I went to O'Reilly's and there was a helpful guy who tried a new relay for the HDM module for me. Nothin. I'm at my wits end here, I've tried new relays, the fuses are good, the headlights are good. Can I try anything else?

In summary, no other electrical issues. The lowlamps are the only issue I have. They haven't come on at all in about a week - so whatever was allowing them to come on intermittently is now fried, I'd guess.

Thanks for the help!
Glad to hear everything is working out for you! Enjoy your Envoy and feel free to post more comments or questions you might have. Thank you!
:)
Joey, GM Customer Service
 

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2008 gmc envoy_sle
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9 Posts
Discussion Starter #8
No, everything isn't quite working out. I can't drive my Envoy at night because the low-lamp headlights aren't working. :D
 

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2004 gmc
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26,181 Posts
Glad to hear everything is working out for you! Enjoy your Envoy ...
A difficult thing to do when he can't drive at night... :rolleyes: :hopeless

No, everything isn't quite working out. I can't drive my Envoy at night because the low-lamp headlights aren't working. :D
Hi! The relay is a solid state one, not a mechanical unit, so it works in silence. It will never click, so listening won't help troubleshoot it. But it was a good idea.

The reason it's solid state is to allow the system to run the low beam lamps at a dimmed intensity for the DRL function.

To go much further, you need to figure out if the problem is upstream or downstream from the relay. Do you have a meter and some electrical troubleshooting experience? If you do, you can dig deeper into the signals at the relay socket. Otherwise it's shotgunning. And there isn't much to shotgun other than the relay.

How did you test the lamps and fuses?

When they go out, was it clearly BOTH sides dying at once? Not one was permanently dead and the other side was the intermittent one?

Anyway, it's been reported that the relay socket can have loose or oxidized connections inside the fuse block, but that should be left for somebody who's dig deeply before. But if you have a meter, it's easy to check out the voltages at the relay socket.
 

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2008 gmc envoy_sle
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9 Posts
Discussion Starter #10
Roadie,

Thanks for the pointers. I tried the listening thing at the suggestion of the guy at O'Reilly's, so it was worth a try.

I can borrow a multi-meter to get some basic readouts on the signal coming through the relay socket, and I assume what this means is that you are saying that if I turn the light switch to OFF and then monitor the signal coming through, when I turn it to manual ON, I should get some kind of electrical signal coming through?

I've tested the fuses by switching the fuses from high-beam to low-beam sockets (same voltage on the fuses) and the high beams still work but low-beams still don't. As far as the lamps, I've not actually tested the lamps because of this: When the low-lamps (intermittently) came on, they both came on, when they didn't come on, they both didn't come on. It wouldn't make sense that it was a lamp issue if a) they both went off at the same time b) they both came on at the same time c) the fact that they keep coming off and on indicates that it is something to do with power being sent to them, whether a control issue, relay issue, fuse issue, or wiring.

My background is computers, so I'm learning here. I'm just trying to avoid an expensive diagnostic bill from the dealership.

So basically, at this point, I'm going to have to bring it to the dealership?

*sigh*
 

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Banned
2002 chevy trailblazer_ltz
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2,762 Posts
I still feel like it's your relay(maybe intermittent).Next time doesn't work,switch it with another(same # relay) and see if it works.
 

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Banned
2004 gmc
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26,181 Posts
Parts stores staff are not trained mechanics or engineers. The guy was a goof if he doesn't know about solid state relays being silent.

The only other identical relay up there is the adjacent black one (45/46). You can always swap those in case the parts store one was bad.

If you can get a meter, get some training from the owner. You need to measure the voltages on the four relay legs while it's plugged in, which is tricky. You need to locate some small wire (22-28 gauge) and wrap 1-2 turns of wire around each of the four legs of the relay, then plug it back in. Then you can measure the voltage on these little stub wires.

The relay has two control pins and two power pins. I don't have a map of which one is which in the socket without doing more research I don't have time for at the moment. Sorry.

Of the four pins, one will have 12V all the time, one will have ground all the time, and when you turn the headlight switch on, the other two should have 12V on them. If you run the engine and get them where the DRL function should be running (ie: not in PARK, but in DRIVE), then the two pins that change state from zero to 12V, should read some voltage in the middle, like 7 or 8 V.
 

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2008 gmc envoy_sle
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9 Posts
Discussion Starter #13
I'll see about testing it the way you've described...
One note I want to make, most of the resources I've read online, as well as the one you mentioned say there are relays to swap. Maybe it's just because the 2008 model something changed, but the HDM relay is totally unique. There are no relays which can be swapped on the fuse block. I'll see about taking a picture here in a bit to share.

Thanks!
 

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2008 gmc envoy_sle
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9 Posts
Discussion Starter #14
First, the diagram.


Here's the fuse block. Note that the HDM Relay is unique unto itself.


Here's the relay in question.


Here's the posts on the HDM relay.
 

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2004 gmc
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26,181 Posts
Oh, yeah. In 2008 they replaced the electro-viscous fan clutch with an older and more reliable design from the 60's. No more fan clutch relay. Sorry. We're just getting used to 2008 owners coming off warranty and locating trailvoy for help.

Someday one of you new guys have to buy the shop manual for 2008 and become the new systems specialist volunteer.

Thanks for the pictures!
 

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2003 gmc envoy_slt
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7,190 Posts
I have a question:

The HDM relay in the drawing (#46) inside the cover, is not in the same position as the actual relay in the picture.

The actual relay is shown in the #45 spot for the fan relay.

Was it accidentally switched? :confused:
 

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2008 gmc envoy_sle
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9 Posts
Discussion Starter #17
Yeah, I'm thinking that happened last night. I switched it back and made sure it was getting connection but to no resolve. If it got switched before, now its got me thinking I need to go back to O'Reilly's and get them to try a new one in the correct position. Good Catch there!
 

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2002 chevy trailblazer_ltz
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4 Posts
Same headlight issue on my 2002 LTZ Trailblazer

Hey "Eliroyale" did you ever figure out your headlight issue. Same thing is happening with my 2002 Trailblazer.

I think it has to do something with a position sensor on my tranny since I can get my lowbeam headlights to come on (sometimes) if I mess with the shifter and drop it into 1 from D.

I know that when you drop it into reverse the lights come on. Also if the parking brake is set, the lights won'come on until the parking brake is released/lowered.

I'm desperate too as I have never seen anything so bizarre as low beam headlights working so intermittently!!!

Marvin in Miami
2002 Trailblazer LTZ
 

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2008 gmc envoy_sle
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9 Posts
Discussion Starter #19
Yeah, TheRoadie helped me out with this. The HDM headlight driver module seemed to be the only issue, so I went to O'Reilly and the technician there tried a brand new module, but put it in the wrong slot. In my pictures, Roadie helped identify that... so I went back to O'Reilly and got another technician to try a new one... in the right slot. This time the headlights came on immediately and no new issues since!

For the record, there was nothing I could do to get mine to come on, shifting, reverse, nothing.

Good luck with your issue, I know how much of a pain that is!
 

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2002 chevy trailblazer_ltz
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4 Posts
Intermittent Headlights

Ok, thanks for the progress report on your Envoy.

I'll go for a new #46 relay and hope that works. I switched the #45 (fan relay) and #46 relay (HDM headlight) and the headlights wouldn't even come on. At least I got them to work intermittently before the swap. So I put them back in their original positions (#45 and #46).

Since both of my relays are Eatons I'm figuring those are the original relays from the factory and someone has already swapped them - meaning that #45 is dead and does no go good to swap into #46 relay position. So I suppose I better buy two new relays.

I just bought the 'Blazer and working out all the bugs. My fuel mileage went up 20% with new plugs and a new filter (not a K&N) - doesn't look like either had been replaced in ten years. Next is the fuel filter and brake pads. I also have to replace the intake and exhaust manifold gaskets.....both leak terribly.

Keep you posted. Thanks for your help.

Marvin
2002 Trailblazer LTZ
95,000 miles
 
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