2002 Envoy Electrical Issues Related to Liftgate

[02Envoy02]

Latest... I did nothing else but suddenly the "new" LGM seems to be working.

The Good
It seems like almost all the liftgate-related stuff works now - plate lights, manual door lock switches for all doors/liftgate, rear wiper, rear washer, Retained Accessory Power, rear defrost. I didn't get a chance to go back and check the old LGM, I'll do that tomorrow.

And since I got a C0550 scan code I'm pretty sure now that the 4WD is not working because I need a new TCCM (notorious in 2002 when battery disconnected) and not more extensive work as the shop led me to believe. I'm confident I could do the labor but could use advice on what I need for a replacement (obviously not a 2002 TCCM) and whether it will need a dealer scan or a relearn/reset I could do myself. Or could I just get one from a junkyard and plug and go? What costs involved?

The Bad
The keyless remote still does not work at all. When I was in AutoZone I tested it and it worked but tomorrow I will try to change out the battery and try again. Do I need to do a relearn/reset procedure when I change that battery?

The Ugly
It's still running like crap with the engine light on and sometimes blinking. I have no doubt this is related to disconnecting the battery ground wire. But the scan I had done says P0305 (see previous post). It has been suggested that I need to clean the throttle body and that the P0305 code is a separate issue and I might check the cylinder 5 ignition coil by swapping with another one and seeing if the problem moves to that cylinder (new scan). I'm not sure I'm up to doing either job myself -- not sure what the coil switch even entails in terms of difficulty. Any thoughts on a next step? Again, I'm convinced the battery disconnect led to this and I'm hoping for some kind of relearn/reset or other next step that is less involved than starting with the throttle body or ignition coils. What about a vacuum leak, is there an easy way to check for that?

Thanks.

 

[DAlastDON]

Latest... I did nothing else but suddenly the "new" LGM seems to be working.

The Good
It seems like almost all the liftgate-related stuff works now - plate lights, manual door lock switches for all doors/liftgate, rear wiper, rear washer, Retained Accessory Power, rear defrost. I didn't get a chance to go back and check the old LGM, I'll do that tomorrow.

And since I got a C0550 scan code I'm pretty sure now that the 4WD is not working because I need a new TCCM (notorious in 2002 when battery disconnected) and not more extensive work as the shop led me to believe. I'm confident I could do the labor but could use advice on what I need for a replacement (obviously not a 2002 TCCM) and whether it will need a dealer scan or a relearn/reset I could do myself. Or could I just get one from a junkyard and plug and go? What costs involved?

The Bad
The keyless remote still does not work at all. When I was in AutoZone I tested it and it worked but tomorrow I will try to change out the battery and try again. Do I need to do a relearn/reset procedure when I change that battery?

The Ugly
It's still running like crap with the engine light on and sometimes blinking. I have no doubt this is related to disconnecting the battery ground wire. But the scan I had done says P0305 (see previous post). It has been suggested that I need to clean the throttle body and that the P0305 code is a separate issue and I might check the cylinder 5 ignition coil by swapping with another one and seeing if the problem moves to that cylinder (new scan). I'm not sure I'm up to doing either job myself -- not sure what the coil switch even entails in terms of difficulty. Any thoughts on a next step? Again, I'm convinced the battery disconnect led to this and I'm hoping for some kind of relearn/reset or other next step that is less involved than starting with the throttle body or ignition coils. What about a vacuum leak, is there an easy way to check for that?

Thanks.

With the engine cold and running spray some carburetor cleaner over the gaskets and hoses. Idle speed will change if the spray gets in anywhere.

 

[Mounce]

Still sounds like a flakey wire. Go open and close the lift gate a few times and see if everything still functions. Stuff doesn't just work one minute and not the next on our rides without it having a bad connection. "But I've already checked the wires" yes I know, but you still have what sounds like a wiring issue.

P0305 is in no way related to disconnecting the battery. Coil packs go out on their own whenever they feel like it.

If you don't feel comfortable cleaning the throttle body or swapping coils, then how are you comfortable swapping LGM's and prodding wires? I'd choose throttle body/coil pack any day over taking body panels off and studying wiring diagrams.

How long did you have the battery disconnected? If it'd been long enough to reset the PCM you'd likely know about it because it would die every time you had the AC on and made a turn at slow speeds.

Either way, clean the throttle body and reset the PCM. The throttle body is as dirty as the bottom of a cows hoof and would appreciate being cleaned whether it's causing problems or not, they get VERY DIRTY but only have issues when the PCM gets reset because then the PCM thinks it's clean when it's not and doesn't tune it right which requires it to be cleaned for it to run right.

 

[02Envoy02]

With the engine cold and running spray some carburetor cleaner over the gaskets and hoses. Idle speed will change if the spray gets in anywhere.

Thanks. Will try and let you know.

 

[02Envoy02]

Still sounds like a flakey wire. Go open and close the lift gate a few times and see if everything still functions. Stuff doesn't just work one minute and not the next on our rides without it having a bad connection. "But I've already checked the wires" yes I know, but you still have what sounds like a wiring issue.

P0305 is in no way related to disconnecting the battery. Coil packs go out on their own whenever they feel like it.

If you don't feel comfortable cleaning the throttle body or swapping coils, then how are you comfortable swapping LGM's and prodding wires? I'd choose throttle body/coil pack any day over taking body panels off and studying wiring diagrams.

How long did you have the battery disconnected? If it'd been long enough to reset the PCM you'd likely know about it because it would die every time you had the AC on and made a turn at slow speeds.

Either way, clean the throttle body and reset the PCM. The throttle body is as dirty as the bottom of a cows hoof and would appreciate being cleaned whether it's causing problems or not, they get VERY DIRTY but only have issues when the PCM gets reset because then the PCM thinks it's clean when it's not and doesn't tune it right which requires it to be cleaned for it to run right.

I suppose there could still be a bad connection somewhere but I don't know what else I can do short of replacing whole harnesses. I've been reading all over the place about some modules and components needing to relearn or reset so I respectfully disagree with your statement: "Stuff doesn't just work one minute and not the next on our rides without it having a bad connection."

Which leads to your question/comment on checking wires and swapping out a module versus taking apart engine parts in a cramped and messy environment -- just something I'm more comfortable and confident with.

As I stated in earlier posts, the battery was disconnected long enough to have the classic fluctuating idle with the A/C on. I'm obviously not driving it around with the A/C on but still runs real rough. And like I said previously, I admit it does seem to be as I remember from a few years ago when I had a bad coil replaced. HOWEVER, this happened EXACTLY when I started it first time after battery was disconnected so whatever the problem is I have ZERO doubt that it was somehow caused directly or indirectly from disconnecting the battery. Luckily, I haven't had the ventilation actuator problem typical with this.

I probably will clean the throttle body or have someone do it. I have been hesitant after reading in a few places that cleaning it is a way to match it to the reset PCM but doesn't really help in the long run because whatever has got to the point of causing the buildup is going to continue -- makes sense to me but only if I can get the PCM to relearn to the current conditions (without cleaning) but I'm not having luck with that so far. Which begs the question, when you say "clean the throttle body and reset the PCM" what do you mean by "reset the PCM," isn't it already reset to thinking it's clean or are there other steps?


A little aside from my For What It's Worth Department... I'm not a big fan of our current society's take on having new technology to the nth degree of every little thing in our lives. I think corporate America jams all this technology down our throats not because it makes our lives better but because THEY CAN to make a buck and arguably it is good for the economy. I'm not saying all technology is bad, I'm just saying look at all these problems I'm having, some just from disconnecting the battery. Sorry, but when working on a car becomes so complicated (or convoluted) you can't even disconnect your battery I don't see that as progress. I would much rather have the simpler engines and vehicles of decades past, I don't really need all this computerized module stuff but do I really have a choice? In short, one of my favorite sayings -- and will go in my signature block if I get around to it -- Just because you can doesn't mean you should.

 

[02Envoy02]

Update …

The “new” LGM is working just great. I switched back and forth a few times the old and new ones – new one works and old one doesn’t. No wire issue – case closed. My liftgate is all back together.

However, my keyless entry still didn’t work. I figured it must be because it needed to be reprogrammed to the new LGM. Did it and it works. I must have read 20 things about replacing the LGM on this site and others and never saw one word about needing to reprogram the keyless entry.

So, I’ve managed to fix the original problem that started all this, the rear wiper and washer not working. Then I fixed the keyless entry resulting from the LGM swap. Now I still have some engine running issues to fix following disconnecting the battery. I am going to clean the throttle body now that I found a pretty good video on doing that (the first video I saw must have been recorded by Muhammed Ali while he was juggling during a blackout). I expect that it will still be running poorly because I got the P0305 code. I tried spraying carb cleaner but didn’t find any vacuum leaks. After cleaning the throttle body I will do the relearn procedure I found in an Article on this site (no one had mentioned that to me yet) then drive it a bit and get another scan for DTCs. Heck, I’m feeling so good I might even take on that monster of all projects – fixing the bad connection on the hood light!

I would still appreciate any input on the TCCM. My 4WD has been out a long time and the indicator light for the switch has been out a long time. Because I got a C0550 scan code I suspect that the 4WD is not working because I need a new TCCM (notorious in 2002 when battery disconnected). I'm confident I could do the labor but could use advice on what I need for a replacement (obviously not a 2002 TCCM) and whether it will need a dealer scan or a relearn/reset I could do myself. Or could I just get one from a junkyard and plug and go? What costs involved? After doing some research I found people having a lot of other transfer case and other problems that I don’t want to get into and is more than I want to spend as I really don’t have a big need for 4WD. So, is there a way I could with a fair degree of confidence determine that replacing the TCCM would likely fix the problem?

One more thought on battery disconnect issues … Maybe it’s out there and I just didn’t find it but since I’m hardly the only fool who has run into this it would sure seem needed to have an article or post just about what problems can occur when you disconnect the battery, how to check for them, and how to fix them. I mean ALL of them. Yeah, I can find stuff on the throttle body/PCM, the TCCM, the a/c vent actuators, (is there more?) but it’s piecemeal – why not someone put it together in one place or at least list where to find the puzzle pieces?

 

[Sparky]

TCCM is easy. Get a used one from a 03 or newer Trailblazer or Envoy ONLY (Buick, Saab, etc are different and will not work right). I got mine from ebay but a junkyard would be fine too. Does not need reprogrammed. Unplug old one from behind the driver side kick panel and plug in the replacement. Done. I had to do that on my 02 when one day it just blinked out and never worked again until I swapped in the TCCM I got from an 05 Envoy.

Since the key fob is programmed to the LGM, it makes sense that after swapping that module that you'd need to reprogram the fobs. Probably would have skipped my mind also though until I tried using the fobs.

I never bothered fixing my hood light. I just give it a whack if I want it to work lol.

P0305 is specific to cylinder 5 (2nd to last towards the back). Pull the coil pack and check it out. If everything looks good (no water etc) swap it with another cylinder and see if it follows. Disconnecting the battery will not cause a cylinder to misfire.

 

[02Envoy02]

TCCM is easy. Get a used one from a 03 or newer Trailblazer or Envoy ONLY (Buick, Saab, etc are different and will not work right). I got mine from ebay but a junkyard would be fine too. Does not need reprogrammed. Unplug old one from behind the driver side kick panel and plug in the replacement. Done. I had to do that on my 02 when one day it just blinked out and never worked again until I swapped in the TCCM I got from an 05 Envoy.

Since the key fob is programmed to the LGM, it makes sense that after swapping that module that you'd need to reprogram the fobs. Probably would have skipped my mind also though until I tried using the fobs.

I never bothered fixing my hood light. I just give it a whack if I want it to work lol.

P0305 is specific to cylinder 5 (2nd to last towards the back). Pull the coil pack and check it out. If everything looks good (no water etc) swap it with another cylinder and see if it follows. Disconnecting the battery will not cause a cylinder to misfire.

Thanks for the feedback. I did fix the hood light as there is an Article on here on how to do it. Pretty easy and much better than playing with it all the time to light up. Also learned something as I'd never seen a gravity-based contact system like that.

What can I expect to spend on a used TCCM?

As for the coil pack, I couldn't even point to it. Do you know of a good article or video on how to remove it?

 

[Sparky]

I paid $80 or so for mine, so I guess around there.

The coil packs are underneath the air intake resonator. When had that off to clean your throttle body you'll see the 6 coil packs all lined up in a neat row there. This should help. https://www.youtube.com/watch?v=DjL_Wefla0s

 

[02Envoy02]

[SIZE=10.5pt]Well, that's it. As in, I'm done. Fixed everything and it's running like new!!! Except for the 4WD but that's a project for another day. Thanks to those who helped me.[/SIZE]

[SIZE=10.5pt]Nothing extraordinary in my efforts but I thought I'd provide a few comments for those who have followed and fellow neophytes as I have the feeling this topic is going to come up in a lot of searches because of the multiple issues addressed. For kicks and giggles, view these photos chronologically (download the zip file, click on the Details and then click Date column to order them chronologically): https://www.dropbox.com/sh/7h82e3eiklaaq0c/AADE_6UOCEBiTERG_GKr23Cfa?dl=0[/SIZE]

[SIZE=10.5pt]Before and during, I reviewed several posts here and elsewhere and watched a few videos. I removed and cleaned the throttle body. Also changed the spark plugs and the coil (not a "coil pack" -- look it up) on cylinder 5. Got my parts at AutoZone: ACDelco 41-103 spark plugs and a Duralast coil. Learned from my AutoZone receipt that I can get a manufacturer's rebate of $2 per plug, good until [/SIZE][SIZE=10.5pt]1/29/16[/SIZE][SIZE=10.5pt].[/SIZE]

[SIZE=10.5pt]Unlike many people I read about, I had zero problems with removing any of the coils or spark plugs. However, I had one bitch of a time removing the coil electrical connectors and I broke the male end on four of the coils. And the male end is epoxied into the coil body (i.e. not meant to be removed/replaced). LESSON LEARNED: Don't remove them if you don't have to. Of course, I had to remove the one from the cylinder 5 coil and I removed the one from cylinder 2 with the intent of swapping them for testing (never did bother swapping, though) and they both broke. The others I removed thinking it would be better to just remove the coils and get them out of my way and not risk having any coils hanging by the wires, plus figured it would be worth checking the connectors. I removed the gray keeper(?) on each connector but still had to use pliers with a lot of force to remove each one. Two of them actually broke on the coil (male) end as in part of the plastic broke into pieces. Luckily, one was coil 5 that I was replacing anyway and the other I managed to tape back together (let's hope it holds). The other two that "broke" had the little tabs break off that lock the female half on. So, I had to get creative with electrical tape and toothpicks (don't ask) to get those connectors secured when reattached. Here's what I think the problem was but realized it too late (and believe me, I went back and checked a few videos and didn't see anybody address this). Just removing the keeper doesn't adequately release the part of the female connector that goes over the tab on the male (coil side) connector. You might have to get a screwdriver under the overlap/hood of the female connector and pop it off the tab. Problem is, if you don't know it's there you won't see it or be able to get to it until you first remove the coil and can basically tip it upside down to look in under the overlap to see the tab. I hope this makes sense, I guess I should have photographed it. RECAP: DON'T remove the coil electrical connector unless you have to. If you have to, remove the coil first, then remove the keeper on the connector, then set the coil down such that you can look into the bottom (overlap) of the connector and pop the female end over the male end tab with a small screwdriver, if needed.[/SIZE]

[SIZE=10.5pt]I didn't have any problems putting in the spark plugs and reinstalling the coils other than securing the connectors as noted above. I put some anti-seize grease on the plug threads (only cost $1.99 for a small packet) although I don't expect to have to remove them again with 237,500 miles already on it.[/SIZE]

[SIZE=10.5pt]Amazingly, started right up and idled smoothly, even with the a/c on. Revved it with no hesitation or obvious missing or other problems. Took it for a long ride in the pouring rain and it ran like a thoroughbred, as well as I remember it when I bought it in December 2002 at an auto auction with 25K miles on it (paid $25K, sticker price was $37K). It would have been interesting to do one repair at a time and see how the Envoy responded but I was more interested in just getting it done and running good. Despite having the vehicle for so long and so many miles, I confess I didn't even know where the spark plugs were before taking on these problems. I have to admit I'm kind of proud of myself for accomplishing this which I can now understand is a big part of being on GMT Nation![/SIZE]

 

[Joseph Gary Jr]

Similar to other threads I've read, I've got problems with my 2002 Envoy (rear wiper and washer out, keyless remote not working, Retained Accessory Power out, license plate lights out -- don't hear any clicking or noises but frankly my hearing is poor). However, I'm currently stuck in my troubleshooting. I didn't find any fuses out (not sure about relays) so I pulled the wire boots in the rear and liftgate and didn't find any broken/frayed wires. Went out and bought a new multi-meter and checked the two orange wires and got 12V against both the black and brown wires. However, the blue wire is a whole another animal. I checked it several times in several places and I swear the voltage varies all over the place -- once in awhile it settled at about 0.2V. All voltage measurements with key off (not even in ignition). Thoughts?

Wondering if I should now go get a used LGM or BCM. I am confused, however, on where these modules are located. I had read somewhere that the LGM is the big thing in the front of the under seat fuse box but now I'm thinking that is the BCM -- maybe it varies by year/model.
But I've also read some people finding solutions related to the liftgate or back window switches and also disconnecting the battery, a fuse or some other component.

Appreciate any help. Thanks.

I'm having same problem with 04 GMC envoy got ticket because license plate light not working disabled on fixed income and could use help with this matter please

UPDATE: As is typical for me, nothing is ever easy. Reconnected the connector and now the license plates lights come on with the parking lights but the other things I've mentioned are still out! I fiddled with the connector and wires and sure enough the plate lights will flicker (but interesting the tail lights don't). BUT I still can't pinpoint where the problem is!!! I removed the interior panel on the liftgate that is closest to the wires near the connector and have about two feet of wires I can get to. Removed about a foot of tape from the wires. But I still can't see any broken or even frayed. I pulled on each wire at different locations but could not come up with any consistency with the flickers except it seems it might be near or in the connector. Of course, I pulled hard on each wire on both sides of the connector but still couldn't pinpoint it. I don't really see how it can be the connector since all wires are firmly connected to the pins and none of the pins are broken but I went to AutoZone to get one and they didn't even have them or seem to know what I was talking about!

This is really getting frustrating and taking up way too much of my time. And note I said that even when the tail lights are on I'm still not getting use of my keyless remote, rear wiper, and RAP.

What can I try next??? Should I just take it to the shop and enter with my arms in the surrender position, wallet in one hand?

i don't know but about to the point of finding a vehicle that old as me no electric vehicle nothing but trouble

 

[Joseph Gary Jr]

Latest... I did nothing else but suddenly the "new" LGM seems to be working.

The Good
It seems like almost all the liftgate-related stuff works now - plate lights, manual door lock switches for all doors/liftgate, rear wiper, rear washer, Retained Accessory Power, rear defrost. I didn't get a chance to go back and check the old LGM, I'll do that tomorrow.

And since I got a C0550 scan code I'm pretty sure now that the 4WD is not working because I need a new TCCM (notorious in 2002 when battery disconnected) and not more extensive work as the shop led me to believe. I'm confident I could do the labor but could use advice on what I need for a replacement (obviously not a 2002 TCCM) and whether it will need a dealer scan or a relearn/reset I could do myself. Or could I just get one from a junkyard and plug and go? What costs involved?

The Bad
The keyless remote still does not work at all. When I was in AutoZone I tested it and it worked but tomorrow I will try to change out the battery and try again. Do I need to do a relearn/reset procedure when I change that battery?

The Ugly
It's still running like crap with the engine light on and sometimes blinking. I have no doubt this is related to disconnecting the battery ground wire. But the scan I had done says P0305 (see previous post). It has been suggested that I need to clean the throttle body and that the P0305 code is a separate issue and I might check the cylinder 5 ignition coil by swapping with another one and seeing if the problem moves to that cylinder (new scan). I'm not sure I'm up to doing either job myself -- not sure what the coil switch even entails in terms of difficulty. Any thoughts on a next step? Again, I'm convinced the battery disconnect led to this and I'm hoping for some kind of relearn/reset or other next step that is less involved than starting with the throttle body or ignition coils. What about a vacuum leak, is there an easy way to check for that?

Thanks.

The number 6 coil and plug are prong to getting water on it when it rains they known for that problem my 04 GMC envoy has 330,000 miles on it and it is nothing but trouble 2 wheel drive and all electric will find old truck to trade for to haul my 4wheeler

 

[Joseph Gary Jr]

Here's what mine looked like, I really had to wrestle that boot out of the way to find it, think I used Vaseline so it would slide easier.
View attachment 66500

I traced my brown wire and nothing foot behind the boot going to tail light still no fire with test light stage 2 transmission with 52,000 miles on it and motor has 330,000 always had miss tack never worked Sense I bought it year ago put 7,000 miles on it and$350 into it time it goes

 

[Joseph Gary Jr]

Latest... I did nothing else but suddenly the "new" LGM seems to be working.

The Good
It seems like almost all the liftgate-related stuff works now - plate lights, manual door lock switches for all doors/liftgate, rear wiper, rear washer, Retained Accessory Power, rear defrost. I didn't get a chance to go back and check the old LGM, I'll do that tomorrow.

And since I got a C0550 scan code I'm pretty sure now that the 4WD is not working because I need a new TCCM (notorious in 2002 when battery disconnected) and not more extensive work as the shop led me to believe. I'm confident I could do the labor but could use advice on what I need for a replacement (obviously not a 2002 TCCM) and whether it will need a dealer scan or a relearn/reset I could do myself. Or could I just get one from a junkyard and plug and go? What costs involved?

The Bad
The keyless remote still does not work at all. When I was in AutoZone I tested it and it worked but tomorrow I will try to change out the battery and try again. Do I need to do a relearn/reset procedure when I change that battery?

The Ugly
It's still running like crap with the engine light on and sometimes blinking. I have no doubt this is related to disconnecting the battery ground wire. But the scan I had done says P0305 (see previous post). It has been suggested that I need to clean the throttle body and that the P0305 code is a separate issue and I might check the cylinder 5 ignition coil by swapping with another one and seeing if the problem moves to that cylinder (new scan). I'm not sure I'm up to doing either job myself -- not sure what the coil switch even entails in terms of difficulty. Any thoughts on a next step? Again, I'm convinced the battery disconnect led to this and I'm hoping for some kind of relearn/reset or other next step that is less involved than starting with the throttle body or ignition coils. What about a vacuum leak, is there an easy way to check for that?

Thanks.

I replaced coils and plugs well 4 coils was told they were replaced just before I got vehicle 7,000 miles I shouldn't have to replace any also replace the Crank and cam sensors used foam to clean throttle body and ac don't pull down motor now but electric system is a nightmare

 

[Joseph Gary Jr]

I replaced coils and plugs well 4 coils was told they were replaced just before I got vehicle 7,000 miles I shouldn't have to replace any also replace the Crank and cam sensors used foam to clean throttle body and ac don't pull down motor now but electric system is a nightmare

And the coil here is $74 each