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Liftgate Control Module Problem

136K views 79 replies 51 participants last post by  Brody5150 
#1 ·
I took my 05 Envoy to GM today to check why the remotes doesnt work anymore, nor does the rear wiper or rear defroster, and also the liftgate does not lock when I lock all doors from inside the car. The only way to lock it is manualy.

The dealership said that the LGM (rear body control module) has gone bad. But they scaned with the computer the car and they said that there is a short circut somewhere in the ground of the car, they showed me a module that is located under back seat on the driver side (where the fuses are) and said they suspect that it caused the module to fail. Any suggestions on this issue

Thanks!
 
#32 ·
More of the same problem-Tailgate wires broken, remote not working

2002 Envoy SLT

Thanks to the various posts about this problem, I have established that I have multiple broken wires on the tailgate lock wire harness, as well as the protective sheathing on other wires that has cracked or been crimped and are now exposing the wire strands inside, which may in time lead to a short. The tailgate now cannot be opened as the power to open the lock has been lost due to the break. I will have to employ the emergency release to get it open again. From the state of the wires in the harness I can see someone has been in there already fixing "stuff". If I carry on splicing wires the whole repair will be enormous and thick and may just break down again very quickly due to the lack of space and the rubber boot that seems way to small anyway.

To my point or question: It would seem prudent to replace all the wires in the harness( I think fives in total) and I may just have to go down this route. Is there an electrical connection point a short distance away from tailgate entry point, that just plugs in, so I do not need to splice in wires, or is the only way forward to go and splice the wires.

Many thanks

Tailor

:hijacked
 
#36 ·
Standard Liftgate Problem

My first time posting, though I do glance through once in a while.

This week, I noticed that my keyfob wasn't working. Then, noticed that the inside domelights would remain on, radio would not retain power, rear wiper stopped working, liftgate lock/unlock didn't work. I wasn't quite sure how to determine if the defogger was still working; and the license plate lights were ok. Read like the standard liftgate control module problem.

After reading the many comments on this site, it was clear that something was wrong with either the LGM or the associated wiring. After reading from someone's comments of how to emergency-release the liftgate (should've know it would be right there in the owners manual), I removed the boot from the liftgate side and didn't notice anything that really jumped out -- even tugged on the wires slightly. Then, removed the boot from the body side ....and an orange wire fell out! It was the thin orange wire (circuit #2740, battery positive voltage) going into the 6-way connector. (I located the circuit diagram from someone else's post on this web site. Thank you.)

As a quick test, I reconnected the ends of the orange wire, temporarily wrapped it with electrical tape and then tried out the keyfob. It worked!! I'll have time tomorrow to make a permanent fix but, I truly appreciate everyone's commentaries. (I've attached a photo of my temporary fix.)
 

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#67 ·
Then, removed the boot from the body side ....and an orange wire fell out! It was the thin orange wire (circuit #2740, battery positive voltage) going into the 6-way connector. (I located the circuit diagram from someone else's post on this web site. Thank you.)

QUOTE]

I realize this is a very old post, but I have the same problem that everyone else seems to have with the lift gate module except my wires appear to be fine, I just have no power on the small orange wire referred to above. If I jumper it to the orange wire next to it (which does have 12volts) everything works fine. I'm a little worried about leaving it like this. I'm sure they made it a separate wire for a reason. Does anyone know where this small orange wire comes from. or know where I can get the schematic?
 
#37 ·
way to flip tailgate DOWN?

Hello, First time poster...
I have been searching this site for info on my Envoy XUV tailgate not opening, and I have made quite a bit of progress. Here is my issue. I have manually opened the tailgate multiple times, but it will only open sideways. In order to access the boot at the hinge point, I need to manually open the tailgate DOWN. I am willing to totally remove the tailgate if someone tells me how, but if I could just get the gate down, I could move on from this headache. Thank you in advance!
 
#38 ·
Hi All,

New user, cross posting from the other liftgate control module thread.

Thank you to all who described and posted photos of the broken wires. I found that the big black wire was broken. You saved me about $300 in parts and programming.

Now the question I'm cross posting:

Has anyone bought a new wire harness from GM and installed it? How did it go?

Thanks!

- Paul
 
#39 ·
I have the same problem. I have checked all of the wires in the rubber boot and they are all intact. No breaks, no cuts, nothing yet I'm am having all of the symptoms you guys are having. No key fob, no wipers, no defrost. I'm at my wits end with issue. I have a warantee with this truck. Does anybody know if this is covered by warrantee or a recall this is certainly a manufacturers defect. Looks like I'm on my way to the dealer. :duh:
 
#40 ·
If it's an aftermarket warranty, all the contracts are different and you'll have to consult its exact written terms.

Are you sure the CONDUCTOR is intact inside the insulation of each of the wires? You really can't be certain unless you run a continuity check from end to end on each wire. That requires access to the schematics. Have you been using them? How about power? Do each of the three wires that need power in the liftgate have it?

At your wits end isn't the end of the world - it just means you need an engineer or experienced electrical technician to troubleshoot it instead of whatever process you've been using. :confused:
 
#41 ·
Youre right. It could be the conductor within the wire jacket. The issue is how do I test for continuity. I don't know where the other end of the wire is. I'm not much for auto electrical other than battery, alternator, starter type stuff and I don't read electrical schematics. Even if I locate a bad wire how do I know there the break is so I can splice it? I was hoping for a few broken wires that I could easily solder together but looks like my issue is a little deeper. Oh well, I will have to spend some money on this one. To the shop it goes...:p
 
#42 ·
The issue is how do I test for continuity.
Acquiring the training and experience for reading schematics could save you a bit of money. But for now, just use the old pin-through-the-insulation trick. Get two small needles or pins. Stick them through the insulation at either side of the flexing part of the wire. Check between the pins for continuity. The hole the pin leaves will self-heal, except for extremely wet places you should wrap over with tape after the test.

Or flex the wire. Ones with broken inner conductors will flex more limply than intact ones.
 
#44 ·
Repaired the wires and nothing!

I have the same problems with my 2003 Envoy. I found the Black, small orange broken and the two large orange insulation frayed, grounding out I am sure. I spliced all connections using environmental splices and tested continuity using the pin method across the splice. Continuity was good and nothing works. Has anyone had to replace the lift gate module after this repair? I still do not know where this is located in the vehicle. If this is replaced does it need to be programed? Can you find used ones?

Any help would be greatly appreciated.
 
#45 ·
The LGM is inside the liftgate. New, virgin ones have to be dealer-programmed at rip-off prices. Used ones can be found.

If you found frayed insulation and suspect a short to ground, then blown fuses are the natural conclusion. I don't have schematics with me at the moment, but check the Owner's Manual.
 
#48 ·
Eureka it worked

Thanks to this forum I was able to diagnose and fix the problem with my key fob, delayed functions, and liftgate functions for free. I had a broken wire in rubber casing connected to the liftgate and the body of the truck. Woo hoo this has saved me well over 250 on repairs. I just dont get if this is something common why dont they recall it and have these wire swapped out.
 
#50 · (Edited)
GoCartbuilder

I'm new to this site. I did not want to start a new thread about Trailblazer Envoy wiper problems so I am posting my problem here. Hope I am doing this correctly. Have a 2005 Trailblazer. Have read most of the threads and have not seen anything like my problem. My rear wiper will only work after having closed the rear hatch. Let me explain further. Upon closing the rear hatch the wiper will work in all speed positions. I can randomly change speed positions at will. (Unless I turn it off, then it will not come back on) If I momentarily turn it-off-on before the wiper has stopped moving it continues to work. However if I turn it off completely it will not turn back on unless I open the rear lift gate and close it. Engine can be running or off as long as the ignition is on. Lift gate, remote unlock, rear washer and license place lights all work. All wires in harness at hinge point are good. Fuses and circuit breaker are all good. Grounds are good. All connectors have been taken apart and cleaned and reset. It seems as though that once the wiper switch is turned to off, memory/power is lost until it is reset by opening and closing the rear hatch. Any suggestions. My guess is the Rear Control Module. What I'm not sure of is: does it need to be replaced or just reprogrammed?
 
#51 ·
LGM issues finally SOLVED

lost all liftgate functions(locks, wiper, defrost)except the license plate lights still worked. Had 12 volts at wiper motor and at the LGM between the orange (power) and black leads. Could not find any problems with wiring inside the boot at the top of the liftgate. Bought a used LGM off E-bay for $25, which comes already programmed. Plugged it in and everything works. Seller stated that the LGM was from a 2009 TB. It had a different part number than my 2002TB had, but works fine. :)
 
#53 ·
My 06 TB SS started with the same problems as others have previously mentioned, so I decided to look at the wires. Sure enough two wires were completely cut in half and two others were starting to fray. I cleaned them up, reconnected them and everything works. I included a cell phone pic below.

 
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#54 ·
I was under the impression that we could not use a used LCM. The older models will use the updated part number when being replaced. I got a couple of the newest version for like 10 bucks each on epay.
I just read this entire post and didn't notice any mention of the power seats or seat heaters not working either. I guess most drivers do not adjust their seats that much.
I have not looked at the wire condition or continuity yet. I will get that when it gets a bit warmer outside.
My biggest issue right now is not being able to open the passenger door for a date. (remotes dont work). I have to open the driver door with the key, then hit unlock inside, then run around and open the passenger door. Sounds silly. Why isn't there a key lock on the passenger door?

Jason
 
#56 ·
Ah HA!!!

I owe this forum soooo much. Bought my '07 TB 1 and a half years ago and have cleaned the throttle body, purchased an ignition switch(cheap insurance), swapped out all the front turn/headlamp/park light bulbs, and adjusted the parking brake (still mediocre-by design).

Just this last week when going to install a viper alarm with the dlpkgm interface I noticed all the classic signs: radio turns off with key(no Retained Accessory Power), rear liftgate won't lock, and the rear window wiper cutout.
After checking the rear wiper c.b, and inspecting the switch I started poking around at that LGM and rear wiper motor.

Now that I've heard all the stories I keep smacking my forehead.
I Spend 8-10hrs a day fixing automotive electrical systems on emergency vehicles. And only after reading this thread and seeing one of the posted pictures do these new quirks make sense.

Thank you all, I'll fix this weekend. This is my do-all family truckster: Kids, groceries, hauls firewood trailer, and everything else.

Long live the GMT360!

:bonk::bonk:
 
#57 ·
Well, I rewired the wiring in the tailgate to body boot and now have power at 5 of the 6 wires at the connector in the tailgate.
Still can't get anything to work.
Unfortunately, I had left the ignition turned on when I was striping one of the small wires (blue I think) and the wire stripper grounded to the frame of the tailgate and caused a short for a short moment. Now the radio doesn't work and the truck won't start or even turn over. the dash lights up and the horn / lights work.
Anyone have an idea if I might have blown a fuse / breaker / relay and if so, which one and where would I find it?
I checked all the fuses under the rear seat and in the fuse panel under the hood. Couldn't find one blown and even swapped fuses & relays with other matching ones.
Any help would be greatly appreciated.
 
#60 ·
This is like the third or fourth item this forum has help me fix on my wife's 2005 trailblazer. Thanks a ton.

First was the oil control valve, saved over $400. :D

Then misfire in cylinder 3. New spark plugs and coil pack on cylinder three saved unknown amount because the stupid dealer could never figure it out. 5 min with a new scan tool, everyone should have one, and I was able to know exactly what the issue was. Unknown why the dealers scan tool didn't see it, or maybe it did and just didn't want to tell my wife.:confused:

Now the tailgate and remote.

Same problem. Remote key lock would not work. Wiper would not work, and so on. Dealer, without even looking at it tells the wife the module is bad and they want $590 to replace and install. Said thanks but no thanks. :no:

A little research back on my favorite Trailblazer forum and had the issue diagnosed in 10 min. Sure enough three wires were cut. A few wire connectors and the Trailblazer is back in business and my wife thinks I'm a genius, once again.:hail:

You would think that with the history of these problems the dealer would be better informed, or more like they are simply refusing to acknowledge it. I would sure like to know from any dealer service employees on here, if there are any, what the heck the deal is, it's like some of these problems they've never seen before. 10 min with the web and this forum and the answer is there.
:thx
 
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