No low beams or DRL, High beams only.

MoMobile

Original poster
Member
Apr 9, 2012
31
( continue from my post here:
No low beams. High beams only. - Page 5 - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum )

The lights on my Mom's 2004 Envoy are going crazy! They do something different every time, but usually it's the DRL/Low beam not working problem.

I have switched the 45 and 46 relay (both have a 15016745 part number on them) as suggested but with no luck. I have also put 4 new 10 amp fuses in for the low and high beam circuits and a 15 amp for the HDM.

Sometimes both lights will work and sometimes only one and it will switch from left to right and/or high to low each time for what will and will not work. Mostly it is just the right high beam but an occasional bump will make the left high beam work for a few minutes.


What else can I try, could it be the switch behind the knob on the dash? What about the AHS (Automatic Headlamp System), could it be the sensor on the dash for that?

I assume the lights on the top are the high beam and the ones on the bottom are low beam, correct?

Signed,
Crazy lights driving me crazy :crazy:
 

Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
tiphat.gif
Welcome
tiphat.gif


In case you haven't
heard:
http://gmtnation.com/f5/welcome-gmtnation-com-heres-story-226/


For the Envoy:

The low beams are high. (top lights)
The high beams are low. (bottom lights)
 

Ace1875

Member
Mar 29, 2012
276
Welcome to GMTNation. from what i know head lights are controlled by the BCM if you know anyone in your local area that has a Tech II besides the dealer i would have them hook it up and check the BCM for issues.

did she leave the back window rolled down during a rain or did the kids spill anything?

My friend's BCM fried on him and nothing was working.

Also from reading your issue it almost sounds like an exposed wire grounding out.
 

Blckshdw

Moderator
Nov 20, 2011
10,706
Tampa Bay Area, FL
Very unlikely to be the switch at fault here. You said sometimes when you bump the truck, the situation changes... :undecided: Where are you bumping the truck? This says to me, you've got a connection issue somewhere, that's changing with movement.

Do you have a multimeter, so you can check for/measure voltages at different points in the headlight wiring system? I would want to check to see if fuses 3 (passenger low beam) and 6 (drivers low beam) are seeing power while this is going on. (Do the same for the high beam fuses 2 & 5) If they both are, then I'd want to check power at the connectors to the headlights. If the side that's out, has power at the main connector, then the issue is something inside the headlight assembly itself... If not, then the issue is somewhere between the fuse block and the connector (wiring issue like Ace1875 suggested)
 

MoMobile

Original poster
Member
Apr 9, 2012
31
Welcome to GMTNation. from what i know head lights are controlled by the BCM if you know anyone in your local area that has a Tech II besides the dealer i would have them hook it up and check the BCM for issues.
No one that I know of but we can take it to GMC if needed to be checked.

did she leave the back window rolled down during a rain or did the kids spill anything?
Not that I know of on either.

Also from reading your issue it almost sounds like an exposed wire grounding out.
The wires that connect to the light bulbs do seem awful thin and dainty.

You said sometimes when you bump the truck, the situation changes... Where are you bumping the truck? This says to me, you've got a connection issue somewhere, that's changing with movement.
I meant a bump in the road, while driving it happens.

Do you have a multimeter, so you can check for/measure voltages at different points in the headlight wiring system? I would want to check to see if fuses 3 (passenger low beam) and 6 (drivers low beam) are seeing power while this is going on. (Do the same for the high beam fuses 2 & 5) If they both are, then I'd want to check power at the connectors to the headlights. If the side that's out, has power at the main connector, then the issue is something inside the headlight assembly itself... If not, then the issue is somewhere between the fuse block and the connector (wiring issue like Ace1875 suggested)
Okay, yes I have a multimeter and need to learn how to use it, I do have a simple test light that I am more familiar with for years.

Thanks for the help and warm welcome. I'll do the electrical test and see what comes up. Maybe I could bump on the BCM to test it? I know that's been done on an ECM before to test it.
 

Ace1875

Member
Mar 29, 2012
276
MoMobile said:
No one that I know of but we can take it to GMC if needed to be checked.


Not that I know of on either.


The wires that connect to the light bulbs do seem awful thin and dainty.


I meant a bump in the road, while driving it happens.


Okay, yes I have a multimeter and need to learn how to use it, I do have a simple test light that I am more familiar with for years.

Thanks for the help and warm welcome. I'll do the electrical test and see what comes up. Maybe I could bump on the BCM to test it? I know that's been done on an ECM before to test it.

those thin and dainty wires are prone to weather wear and exposing them self and grounding out. to reach the BCM you will have to remove the backseat to access it...too much work to start your diagnosis.

I would start from checking for shorts under the hood. A simple test light might help u behind the headlight on it harness. a short could be inside your headlight assembly unit from heat damage. YouTube has a very nice tutorial on how to read and work a multimeter. better then what we can explain it to u.

Also has she helped anyone jump start from her Vehicle?

View attachment 20236
these wires could have melted out from inside of the headlight assembly. unplug that harness and check that harness first.
View attachment 20237
this harness
 

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MoMobile

Original poster
Member
Apr 9, 2012
31
I would start from checking for shorts under the hood. A simple test light might help u behind the headlight on it harness. a short could be inside your headlight assembly unit from heat damage.
When you say, "under the hood", do you mean those aforementioned fuses?

YouTube has a very nice tutorial on how to read and work a multimeter. better then what we can explain it to u.
Thanks, I'll go look it up, I've fiddled with this thing and can't figure it out.

Also has she helped anyone jump start from her Vehicle?
I have jumped my GM car from her truck, but the light problems had already started a long time before that day.

these wires could have melted out from inside of the headlight assembly. unplug that harness and check that harness first.
Okay, will it just have two connectors, as in a negative and positive?
 

Blckshdw

Moderator
Nov 20, 2011
10,706
Tampa Bay Area, FL
MoMobile said:
When you say, "under the hood", do you mean those aforementioned fuses?

That's where I'd start. When one of the bulbs is out, trace through the system for that side and see where you stop getting a power reading, and troubleshoot from that point.
 

Ace1875

Member
Mar 29, 2012
276
MoMobile said:
When you say, "under the hood", do you mean those aforementioned fuses?


Thanks, I'll go look it up, I've fiddled with this thing and can't figure it out.


I have jumped my GM car from her truck, but the light problems had already started a long time before that day.


Okay, will it just have two connectors, as in a negative and positive?
i would start off by removing my headlight on one side pull this harness off
View attachment 5886
then grab your test light and turn your low beams on and test if the yellow wire (left headlight) or tan/white (right headlight) has constant power going to it.

that would be the easiest thing todo. if they do have a constant power on both sides then turn ur high beams on and test them (gark green/white on left side and Light green/black on right side)

now if all of them have a good constant signal then look in your headlight for a short.
 

MoMobile

Original poster
Member
Apr 9, 2012
31
Okay thanks, it's clear now what to do, I'll report back with the results. Thanks again for all the help.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Welcome! I think I was the one who gave you the heads up that we'd all moved.

Any time you have the two lights doing different things, side to side, it can't be the relay or the BCM or the automatic headlight control because thuse items act on both sides at the same time.

Shorts from a power feed wire that has 12V on it, to ground, usually blow fuses. OPENS are the right term for wires that fail to carry power to the destination, mostly due to overheating in the wimpy headlight connectors that causes oxidation or melted plastic that allows the springiness of the contact to be compromised. Many owners end up replacing the headlight connectors with better (high temp) versions from the parts stores.

Another possible issue is that the power feed is OK, but the left and right headlight assemblies might have corrosion or flakiness on their GROUND side (black wires). Eash side has a different connection to ground. I can be misleading if you use a test light OR a multimeter on the power wires to the headlights, you find 12V where you expect to, but you place the ground side of your test light or meter on a good ground part of the body or frame near the headlight. The headlight might be dark because ITS ground is not a good ground, even though you put your test light on a good ground. Putting the test light ground on the headlight's black wire is a better test. Another one if you know a bit of electrical theory is to put the ground side (usually a black wire) of the test light or the meter on a good ground, then put the other end on the black wire coming out of the headlight connector. If you find 12V using that connection, then you can be sure the headlight ground circuit is bad (open).
 

MoMobile

Original poster
Member
Apr 9, 2012
31
check fuse 3, 6, 2, & 5
All have power.

This is what I found, the weather pack that is pointed to in this picture below is very hot and when I wiggle it (on both sides) the lights work (both low and high beams). I did not completely pull the lights or test each wire with the test light because I feel that it needs new wires/weather packs. There was also black electrical tape on both of the weather pack/wire ends from about 6 or so months ago when a local (non-GM) shop "fixed" the lights. When I started the truck all the lights were working but by the time I parked it only the left low beam and right high beam was working, I gave the driver's headlight a bump with my fist and the light came on again. I really think it's just the weather packs/wires, if y'all want me to pull them and test each one okay, I can do that too.

If y'all agree that the wire ends need to be changed, where can I get them?

5886d1334059096-no-low-beams-daytime-running-lamps-high-beams-only-hlgenv07aro_lights_gmc_envoy.jpg
 

Blckshdw

Moderator
Nov 20, 2011
10,706
Tampa Bay Area, FL
ACDELCO Part # PT1136 on Rockauto.com for $25 You might check elsewhere to see if you can get it cheaper.
 

Ace1875

Member
Mar 29, 2012
276
MoMobile said:
All have power.

This is what I found, the weather pack that is pointed to in this picture below is very hot and when I wiggle it (on both sides) the lights work (both low and high beams). I did not completely pull the lights or test each wire with the test light because I feel that it needs new wires/weather packs. There was also black electrical tape on both of the weather pack/wire ends from about 6 or so months ago when a local (non-GM) shop "fixed" the lights. When I started the truck all the lights were working but by the time I parked it only the left low beam and right high beam was working, I gave the driver's headlight a bump with my fist and the light came on again. I really think it's just the weather packs/wires, if y'all want me to pull them and test each one okay, I can do that too.

If y'all agree that the wire ends need to be changed, where can I get them?

5886d1334059096-no-low-beams-daytime-running-lamps-high-beams-only-hlgenv07aro_lights_gmc_envoy.jpg

Hmm. as roadie and i suggested i would test the wires in them to see if a feed is coming through to them. by removing the headlight assembly you will also see if the actual bulb wires are bad also.

I have come across a TB that had a bad weather pack harness but his issue started because the internal wires from inside the lights were burnt out. If this has happen in your case, just fixing those external wires wont solve the issue 100%, but would be a start.

I recommend checking the feed to all the wires, including the ground. this will tell you if the feed to them is still good or not. Then on the headlight assembly off the truck, remove the headlight bulb from the harness, push in two paper clips and feed a 9v battery and test to see if the wires return back a current to the headlight side of the weather pack harness. Make sure you do not have the headlight connected to the truck's harness when u do this test.

A few good MM has a loop back feature, if your does great u can just jump it and see.

Doing this will let you know if the wires inside the headlight are burnt out or not. if you get a feed gently tap and shake the headlight to see if the connection is broken.
 

MoMobile

Original poster
Member
Apr 9, 2012
31
Okay, thanks for the help guys, I've showered already and put the tools up so it will be tomorrow for the next update.

A few good MM has a loop back feature, if your does great u can just jump it and see.

This is what I have, I watched the video on YouTube and it didn't help much. I understand +, -, volts, and amps but that's it. The rest I'm learning, I'm afraid I would need a step-by-step idiot guide on how to use this multimeter on the truck.

Sears: Online department store featuring appliances, tools, fitness equipment and more

View attachment 20245
 

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Ace1875

Member
Mar 29, 2012
276
[video=youtube;0xETtylidWU]http://www.youtube.com/watch?v=0xETtylidWU[/video]

[video=youtube;Wslo0QSrs58]http://www.youtube.com/watch?v=Wslo0QSrs58[/video]

[video=youtube;3IUF2o97a1M]http://www.youtube.com/watch?v=3IUF2o97a1M[/video]

It easy to check for broken wires in your car, and even to find break, if you're equipped with a multimeter and the wiring diagrams. If you don't have a audible continuity test, you can use the lowest Ohms scale and look for resistance below one Ohm.
 

MoMobile

Original poster
Member
Apr 9, 2012
31
Hello all, I got the 9V batter, test light, and multimeter and went right to it.

I found good power and ground on all wires from the harness but some had to be wiggled to get it to work.

I tested the head light assemblies and everything was good except the right low beam, and it had be repaired before (I assume by the shop that "fixed" it); there was a non-GM connector there, taped wires, and chrimped connector. Needless to say, it was bad and there wasn't any continuity on it. The wires inside the head light assemblies were thicker than the truck's harness.

Now I'm back to needing to know where to get those wires/weather packs for the harness connectors. Does it have a connector that I can back track to and just unplug it to replace or am I going to have to splice each wire?

Thanks!
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Most parts stores have that connector, and you have to splice (solder and heatshrink are the best) each wire. The wiring harness goes without interruption right from the headlights to the fuse block.
 

MoMobile

Original poster
Member
Apr 9, 2012
31
Blckshdw said:
ACDELCO Part # PT1136 on Rockauto.com for $25.

What about this one? It almost looks, from the picture, that you feed the wires into it and then snap it together, unless I'm mistaken.

the roadie said:
Most parts stores have that connector, and you have to splice (solder and heatshrink are the best) each wire.

I have experience with solder and heat shrink so I'm good to go there. Too bad there isn't an upgrade for the size of the wires, they seem too small.
 

MoMobile

Original poster
Member
Apr 9, 2012
31
Blckshdw said:
ACDELCO Part # PT1136 on Rockauto.com for $25 You might check elsewhere to see if you can get it cheaper.

Okay, is this for sure the right part to replace the headlight connector? because I am ready to try this now.
 

Blckshdw

Moderator
Nov 20, 2011
10,706
Tampa Bay Area, FL
MoMobile said:
Okay, is this for sure the right part to replace the headlight connector? because I am ready to try this now.

If you go to RockAuto, and put in the part number, they have pics of the connector, so you can eyeball it to be sure it's the one you want :thumbsup:
 

MoMobile

Original poster
Member
Apr 9, 2012
31
Well the picture looks the same but it doesn't say anywhere about it being for the lights, in fact it says it's an engine connector. This website (actually you) is the only source I have telling me it is that part number. I just wanted to be sure it's the correct part before spending $60 on them.
 

Blckshdw

Moderator
Nov 20, 2011
10,706
Tampa Bay Area, FL
MoMobile said:
Well the picture looks the same but it doesn't say anywhere about it being for the lights, in fact it says it's an engine connector. This website (actually you) is the only source I have telling me it is that part number. I just wanted to be sure it's the correct part before spending $60 on them.

:confused: Engine connector? Didn't see that on there, however a number of the connectors in our vehicles are used on many different items and are interchangeable. :yes:

If you don't trust the part number method, use the expandable tree in the Parts Catalog. Here's the path you want to take. GMC -> 2004 -> Envoy 4.2L... -> Electrical-Lamp & Socket -> Headlamp Socket, then scroll down until you find the image that looks like what you're looking for. All the info is at your finger tips, just have to familiarize yourself with the tools. :cool:
 

MoMobile

Original poster
Member
Apr 9, 2012
31
Thanks, that helps; it says that it's OEM part number 15306009, I guess I could call the dealer to be certain.
 

MoMobile

Original poster
Member
Apr 9, 2012
31
I don't need the connector to bulb wire (inside the housing), I need the connector to assembly wire (outside the housing). There is nothing wrong with the headlight socket wire, it's the outside weather pack that is bad. If you read this whole post you'll see that I test them and the results.
 

MoMobile

Original poster
Member
Apr 9, 2012
31
A follow-up to the headlight problem on my Mom's Envoy.

Thanks to everyone here that helped. The paper clip and battery trick to test the bulb sockets was very helpful, this let me know the passenger side assembly wasn't any good.

I replaced ACDELCO Part # PT1136, as advised, on both sides. The factory wire was 22 gauge and the replacement was 18 gauge. GM should be ashamed to put such a high amp thing as a headlight on a small wire like that.

Anyways, after replacement of both sides of the wire harness (PT1136) and a new bucket on the passenger side, it's all working now.

Thanks again to all of those who helped!
 

MoMobile

Original poster
Member
Apr 9, 2012
31
Head lamp:
Pull up on the two brackets circled in yellow.
Pull the head lamp assembly toward you.

Weather pack:
The weather pack is circled in yellow, it is 4 wires, wiggle the wires with the low beams on and if they flash on and off (as mine did) then you know it is this weather pack that is bad.

Repair:
I got my replacements for $26 each at rockauto.com and take note that the replacement is not colored as the original.

ACDELCO Part # PT1136
OEM part number 15306009
 

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