2002 Envoy Electrical Issues Related to Liftgate

[02Envoy02]

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.

 

[Mounce]

Grab what you can on both ends that you can reach on each of the wires and pull them. (if you don't understand that let me know, don't want you to inadvertently pull wires loose in the depths of the lift gate)

Sometimes the wires break internally from the repeated bending from opening and closing the hatch so a visual inspection sometimes won't cut it.

 

[Blckshdw]

The LGM is inside the lift gate, the BCM is under the rear seat attached to the fuse block. Without checking the wiring diagrams, I believe the blue wire is for the Class II Data bus, so you will not see a consistent voltage there, as that's only for transmitting data between the computers.

If you are seeing power on the appropriate lines inside the lift gate, I would say check your grounds for continuity. That could be your issue as well.

 

[Denali n DOO]

It took me 2 attempts to find the broken wire in the rubber boot, they are kind of tight in there. I'll bet you have a black wire broken. the ground is in the rear hatch on the drivers side below the rubber stopper. you can look through the vents on the panel to see it.

 

[02Envoy02]

In response to the three replies I've received so far ...

I'm no electrician, mechanic, or artist. But I have a little knowledge in each area so I measured some voltages and made the attached drawing. I'm frankly befuddled on the strange voltages from the liftgate orange wires (why should there be ANY voltage if disconnected from the main body???)

All the wires I see (including sliding the boot an inch or two either way) look in great condition. And wouldn't at least the ones coming from the main body (and through the boot) have to be okay since I'm getting 12V from both orange wires to the black or brown wires?

I did locate the ground wire attached to the main body just above the liftgate rubber stop on the driver's side and it appears attached firmly. I did a continuity check from there to the black and brown in the connector end from the main body (both good) and voltage to each orange wire (12V). However, when measuring continuity to the brown and black from the liftgate connector end, more bizarre readings; same for that lower left orange wire when checking voltage (see attached diagram).

Can someone provide some details on the next logical step for me?

Thanks.

 

[Blckshdw]

I would suggest downloading the service manuals, have a look at the wiring diagram PDF, that way you know which wire is for which function, so you can better troubleshoot what's (not) going on.

Need service manuals? Get them Here!

 

[Denali n DOO]

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.

 

[MAY03LT]

The pin out on that connector can be tough to find since it's not shown in some LGM diagrams.

Brown should show 12v when the park/head lights are on.

 

[02Envoy02]

Screenshot (96).png

The pin out on that connector can be tough to find since it's not shown in some LGM diagrams.

Brown should show 12v when the park/head lights are on.

Thanks for that diagram. I've read where some like this have 3 orange wires, I only have 2.

I would suggest downloading the service manuals, have a look at the wiring diagram PDF, that way you know which wire is for which function, so you can better troubleshoot what's (not) going on.

Need service manuals? Get them Here!

I'm thinking in my last post I provided enough information for someone in the know to tell me what the likely problem is and what to do next. I'm afraid a book full of wiring diagrams is not going to help me but I could handle looking at a specific wire/component or two.

 

[MAY03LT]

So in your test of the connector coming from body
orange A to black 12.2
orange C to black 12.2

The oranges are B+ feeds to LGM and black is ground to LGM, license lights, defroster and wiper. For now I would focus on the black wire.

There are a few ways to approach this. I would plug the connector back in, and jump the black wire (either side of connector) to a good ground and see if license lights and rke come back. I'm only suggesting this first since nothing has to be removed.

Also no prob on pinout I just went through this the other day and had a tough time finding it.

 

[02Envoy02]

So in your test of the connector coming from body
orange A to black 12.2
orange C to black 12.2

The oranges are B+ feeds to LGM and black is ground to LGM, license lights, defroster and wiper. For now I would focus on the black wire.

There are a few ways to approach this. I would plug the connector back in, and jump the black wire (either side of connector) to a good ground and see if license lights and rke come back. I'm only suggesting this first since nothing has to be removed.

Also no prob on pinout I just went through this the other day and had a tough time finding it.

Good idea. I'll try this tomorrow (well, later today now) and let you know. I usually just pay the shop to fix my vehicle but I'm low on dough AND I have no doubt this is one of those problems where they will bankrupt me over something I could do much cheaper myself ... with help from folks like you.

 

[02Envoy02]

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?

 

[Mounce]

I still think it's an internal break of a wire. No idea on how to pin point it though, most guys have good results with the pull method but I see you didn't.

 

[coolasice]

Thanks for that diagram. I've read where some like this have 3 orange wires, I only have 2.

LWB has 3, SWB has 2


did you try jumping black wire to ground? My money is on a broken ground somewhere between the splicepack behind the side panel and the connector. it may be hard to find as it could be making partial contact (which might be enough for the lamps to illuminate) but not good enough contact to function the wiper+lgm.

 

[02Envoy02]

LWB has 3, SWB has 2


did you try jumping black wire to ground? My money is on a broken ground somewhere between the splicepack behind the side panel and the connector. it may be hard to find as it could be making partial contact (which might be enough for the lamps to illuminate) but not good enough contact to function the wiper+lgm.

It's a wet mess out there today so I will wait until tomorrow and try this. With my luck, I probably need to try it at the exact "Pi Moment" tomorrow. https://gma.yahoo.com/pi-day-circle-calendar-once-century-day-coming-200631540--abc-news-topstories.html?bcmt=1426279101006-fc48cb99-c20b-404e-ae08-2fd6c9d9b4ee

Hey, where in Maine ya at? I lived in Maine three different times but not since 1991. Man, you got CLOBBERED with snow this season. My best buddy lives in Bangor and just got back from his annual winter camping trip to Daicey Pond in Baxter Park (I've gone three times before I got old and fat!) Now I'm in Tennessee - go figure. --- Sorry if this is too off topic. New to the forum so if I'm violating rules let me know. Just wanting to make a little personal connection here for a moment, will get back to my problem tomorrow.

 

[coolasice]

im near the presque isle area. we didnt get the huge snowfalls that bangor and south got. we have more snow overall but it was spread out over a longer time.

 

[MAY03LT]

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?

At the liftgate module there are several connectors. The one you want is the 4 pin - you'll find the two orange wires and a black wire in there. With the 6 pin connector plugged in, see what you have there. The tests will be the same, 12v on oranges and ground on black.

As noted above, sometimes wires break inside the insulation and the fault isn't obvious by looking at it.

The problem with taking it to a shop is you just don't know who will working on your ride. Some guys on this forum, who aren't mechanics for their day jobs, have more skills then people who are.

 

[02Envoy02]

im near the presque isle area. we didnt get the huge snowfalls that bangor and south got. we have more snow overall but it was spread out over a longer time.

I lived in the Bangor and Portland areas but I've been to Presque Isle. In fact, I spent a week there one day.

 

[Denali n DOO]

At the liftgate module there are several connectors. The one you want is the 4 pin - you'll find the two orange wires and a black wire in there. With the 6 pin connector plugged in, see what you have there. The tests will be the same, 12v on oranges and ground on black.

As noted above, sometimes wires break inside the insulation and the fault isn't obvious by looking at it.

The problem with taking it to a shop is you just don't know who will working on your ride. Some guys on this forum, who aren't mechanics for their day jobs, have more skills then people who are.

I just wanted to say your bang on MAY! I'm very far from being a mechanic. My biggest issue is lack of experience and tools. After trying to fix this exact lift gate issue myself I gave in and took Denali to the dealer. I read the threads here and knew most likely what the issue was. The dealer told me I needed a new LGM because mine had failed and a new latch as mine was seized and not moving very well. $201.65 for LGM and $178.00 for the latch, total repair $761.00. Plus I had to pay for their 1 hour diagnosing, $123.65. I told them no you're wrong it'a just a bad ground. Find the bad ground! No, we already diagnosed as per the estimate. I went at it again in the boot and tugged those wires a little harder than before and pulled that black wire right out. Maybe the insulation still was attached a bit, the break was right at the curved flexing part of the wire. Anyways a bit of solder and some shrink tube costing maybe a $1.00 and it was fixed, I just saved $885.00 that the dealer didn't get. When I showed them my repair the next day they had no problem to give me back the $123.65 diagnosing I had paid. It has worked fine since May 2012.

tech comments for correction were; "check lift gate operation, circuit test, lock cycles, scan test, check ajar switches, ok. Check lock actuator, weak, partial movement. Check LGM, loss of communication with ign on, okay with key off. Check wiring, ok. Faulty module, est supplied."

The GM trained tech failed the check wiring part and me the non mechanic fixed it, with the help of the members here.

 

[02Envoy02]

Okay, I don't doubt the possibility, still, that it is a broken wire. But I'm not seeing any real direction from anyone on how to find it. Yes, Denali, I used vaseline on the boot days ago and can slide that puppy all the way left and right in a heartbeat and find no broken wire. And yes, I totally agree on avoiding bringing it to the shop if I can.

I will do the measurements suggested and report results. Other that that, the only thing I can think of is to pierce points in each wire and measure for continuity while having a second person wiggle and pull the crap out of the wire. I am hoping someone has an easier method but that's all I can think of.

I could also just cut out about a foot of the five wires exposed and replace them but then I have to find another 6-point connector (AutoZone didn't have one), and buy wire (not very practical to buy five different colors and gauges but I could), and crimp/connect five wires at four points (counting both sides of new connector).

Will update tomorrow. I'm determined now, this thing ain't gonna whip me!

 

[DAlastDON]

Makes probing wires a breeze. Bed of nails.

 

[Mounce]

I had also thought about just replacing the wires but that'd be the last straw I'd say. Btw solder is more secure and provides a better connection than crimp connectors.

Also, I find no dire need for the connector being there simply because: how many times have you removed your lift gate and how many times do you plan on removing it? Likely zero. If down the road you needed to remove it, slap two pieces of tape on each wire and label them 1-5 so that you can reconnect them easily without getting them mixed up.

But, I'm sure someone would frown upon that...

I'm sure one of the fellas here can find you the OEM connector through an online vendor though.

 

[02Envoy02]

Makes probing wires a breeze. Bed of nails.

For the first time I wish I had a 3-D printer!

 

[Texan]

How about a jumper wire from the black connection to a good ground?
Or use a ohm meter from the black connection to a good ground and
wiggle/pull on the black wire. Connection at LGM.

 

[coolasice]

How about a jumper wire from the black connection to a good ground?
Or use a ohm meter from the black connection to a good ground and
wiggle/pull on the black wire. Connection at LGM.

Yes... been suggested twice yet he has yet to try...

wait...you have power on one side of the connector but not the other? is the connector melted/burnt inside? did you measure that with the two connectors plugged together or separate?

 

[02Envoy02]

Whoa, whoa, whoa, everyone is jumping to conclusions! No burnt wires or bad connector and jumping the black wire to body ground changes nothing. Here are the latest details (better get popcorn and a drink)...

I started again today with everything connected. Turned on parking lights and license plate lights also came on. But keyless entry (remote, FOB, whatever you want to call it) doesn't work and neither does RAP. Also, connected black wire from connector to main body ground, no difference.

I then disconnected battery. Checked continuity across each pin of connected body-to-liftgate connector and all had perfect continuity. (I had fiddled a little with the connector pins and think I fixed the loose connection I reported earlier where the plate lights would flicker. Will check again with battery connected.)

Battery still disconnected... I pulled off the liftgate interior panel (what a pain in the ass) so I now have complete access to the LGM and all liftgate wires. Pulled LGM 4-pin connector and checked continuity of each wire (orange, purple, orange, black) back to body-to-liftgate connector (liftgate side) while disconnected. All had perfect continuity (and yes, I wiggled the shit out of wires while checking). Note that the purple has perfect continuity with the black and no others. Also checked for shorts by checking each wire for continuity with each other wire (i.e. different colored wires) from one connector to the other and, as expected, there was no continuity EXCEPT I noted there was continuity with slight resistance from the purple to brown and from black to brown. For kicks and giggles I measure the resistance as ~4 ohms and ~3 ohms, respectively -- not sure what that indicates (i.e. good or bad?)

Battery still disconnected... With either the body-to-liftgate connector connected and/or the 4-pin LGM connector plugged back in it's a whole another ballgame! All kinds of strange (variable) low voltages can be measured -- remember, the batter is still DISCONNECTED. Apparently some charged circuits remain. (You guys didn't tell me about that, would be nice to know when I'm making measurements!!)

Battery connected. No longer seems to be a loose connection, couldn't duplicate flickering plate lights wiggling/pulling wires and connector. Measured the orange wires to black on the 4-pin LGM connector as advised, each measured 12V as expected. Meanwhile, still no remote operation or RAP.

Other strange phenomena and miscellaneous stuff to consider... With the meter set in sensitive settings (2V and 200 mV), I notice just waving the probes around in the air I was getting variable readings. Does this set to either DC or AC. I thought maybe the probe connections to the meter were a little loose but nope as touching them together I get a constant 0 as expected. I'm doing all this in my carport on a humid day about 50' from the nearest powerline. Been years since I last used a meter but don't remember this. Strange..........

With everything reconnected I started her up to charge for a bit since I haven't done so all week. As it warmed up and kicked down the idle I was surprised that the idle started fluctuating from ~700 RPM to ~400 RPM for a second every 5-10 seconds. Even stalled once. Hadn't been doing that. (Of course, I'm thinking at this point, "What the hell did I do now?!") I happened to turn of the heater and noticed the fluctuation immediately went away and the idle settled at 600 RPM (normal). Turned the heat on/off and idle kept fluctuating every time while on. With heat off, I tried several other items (radio, moonroof, etc.) but nothing else affected the idle.

May be worth noting that shortly before all this began (started with noticing rear wiper not working), I had a new starter installed at the shop and also jump started a car. No idea if related but I'm always skeptical of coincidences.

Okay, what next? Should I be focusing now on the LGM or the BCM? Believe me, I'd much rather find a broken wire but I haven't.

 

[coolasice]

measure resistance from black wire at lgm connector (while disconnected) to ground behind side panel inside rear cargo area. measure resistance from orange wires to large power terminal under rear seat.. they should all be under 10ohms and not change when the wires are pulled on. the blue wire goes to a splice pack under the carpet under the right rear seat. if the blue wire is broken nothing (besides lights) will work as that is the data comms wire.

the fluctuating idle could be a dirty throttle body... they reak havoc if the battery is unplugged while they are dirty.

 

[02Envoy02]

measure resistance from black wire at lgm connector (while disconnected) to ground behind side panel inside rear cargo area. measure resistance from orange wires to large power terminal under rear seat.. they should all be under 10ohms and not change when the wires are pulled on. the blue wire goes to a splice pack under the carpet under the right rear seat. if the blue wire is broken nothing (besides lights) will work as that is the data comms wire.

0.2 ohms from black LGM connector to body ground. Same as to black on liftgate/body connector. I don't have leads that will reach from LGM to under rear seat and I don't really know what you mean by "large power terminal" -- is that connected to/part of the under seat fuse box? Blue wire must not be broken as, like I said, I'm getting heat, radio, etc.

the fluctuating idle could be a dirty throttle body... they reak havoc if the battery is unplugged while they are dirty.

Okay, what do I do about this? How do you avoid the problem when you have to unhook the battery (as I'm assuming the shop did to replace the starter)? Why would that be related to the heater being on?

 

[coolasice]

0.2 ohms from black LGM connector to body ground. Same as to black on liftgate/body connector. I don't have leads that will reach from LGM to under rear seat and I don't really know what you mean by "large power terminal" -- is that connected to/part of the under seat fuse box? Blue wire must not be broken as, like I said, I'm getting heat, radio, etc.


Okay, what do I do about this? How do you avoid the problem when you have to unhook the battery (as I'm assuming the shop did to replace the starter)? Why would that be related to the heater being on?

The large power terminal is the main feed wire to that fusebox. The blue wire is the communication wire, it connects all computer systems together, if the wire was broken between the splicepack and the liftgate connector, everything would work except the lgm (which includes rear wiper, keyless entry, hatch lock, and rear defrost).

If the heater was on it could command the ac compressor on which would account for the idle changes. To avoid, clean the throttle body before reconnecting battery.

 

[Texan]

If you go to section "News & Support", "Articles Submission", and scroll down
you can find a article "How to clean throttle body".

 

[02Envoy02]

The large power terminal is the main feed wire to that fusebox. The blue wire is the communication wire, it connects all computer systems together, if the wire was broken between the splicepack and the liftgate connector, everything would work except the lgm (which includes rear wiper, keyless entry, hatch lock, and rear defrost).

If the heater was on it could command the ac compressor on which would account for the idle changes. To avoid, clean the throttle body before reconnecting battery.

Okay, thanks for the help but I really feel this has turned into a wild goose chase. I'm not seeing any bad wires and would never suspect one under carpet under a seat.

Certainly there are experts on here who have more direct experience with this problem. I just read a few other cases online where people had this problem suddenly occur after having other work done such as replacement of a door switch. Unfortunately, none I read about had any resolution information. I'm beginning to think more and more that my problem is related to when the shop replaced my starter. Or that the LGM really is bad. Certainly someone on here can tell me more about this.

 

[coolasice]

Its your money if you want to take it somewhere. I was merely telling you how to diagnose the problem. The dealership will do these same steps but only after attempting communications with their scantool. Or, you could get a used module from a yard and hope it fixes the problem.

The only thing the shop would have done when replacing the starter was disconnected the battery.

 

[Texan]

Can you go to a "pick a part" yard and get a LGM to try? They can effect
the data line (blue wire) which will effect other items such as RAP and
remote key lock.

 

[02Envoy02]

Can you go to a "pick a part" yard and get a LGM to try? They can effect
the data line (blue wire) which will effect other items such as RAP and
remote key lock.

Like I said earlier, seems like nothing ever goes the easy way for me...

Here's where I'm at. I'm done checking wires. Couldn't find any bad and no one provided to me any feedback on the strange voltages I was getting. I taped up all the wires, shoved them back in the portholes, and plugged them up.

I went to a junkyard and got an LGM from an '04 Trailblazer -- $25 (removed myself). Exact same part number as on my '02 Envoy (15071153). The guy there said it should work without needing dealer programming (which he said was $54) because it's the same part number. Nope. Didn't fix electrical problems. BUT I did notice that when I plug it in (juice it up) that the latch (or something) clicks. The Envoy LGM doesn't do anything when I plug it in. So, does it need dealer programming or is it bad or is it some other problem? Is there a way for me to check it or "reset" it?

The Envoy continues to run like shit since I disconnected the battery. I know folks have said I need to clean the throttle body but I can see that being just the kind of thing where I'll somehow create another problem (or that won't be the solution). I read where some people have supposedly had some success driving for 30 minutes or so where the appropriate sensor resets to current conditions. By the way, now the Check Engine Soon light stays on (blinks on/off every so often) and the Service 4WD light stays on (not really surprised since I was told a while back that I need a transfer case or some other work, surprised it wasn't on sooner).

So, on the way to the junkyard I stopped at AutoZone and picked up a can of Seafoam and put it in the tank. I also had them do an analysis and some codes came up (see attached). I realize these are not always correct and the tech said to check first for a vacuum leak. Drove about 30 minutes each way to the junkyard, still ran like shit when I got back. Funny (not really) that it is running as I remember when I had an ignition coil problem and that happens to be one of the codes. Hard to believe completely new problems are coming up (as I said earlier, I don't believe in coincidences). So, it looks like I'll be cleaning the throttle body (yuck) but not until I try one more thing that I found on the web (yeah, I'm skeptical, too): "after replacing battery need to leave back lift and drivers door open and battery disconected for approx. 5-15 min. then all is FINE!! (this from a mechanic who happened to stop in to said parts store). rmps may still fluxuate for approx 30 miles or maybe a day to day 1/2 depends on driving. hope this helps somebody."

I also pulled a few fuses and rechecked them, all good. Any ideas???

 

[02Envoy02]

Surely there is someone in GMT Nation who can help me solve my problem.

http://gmtnation.com/forums/topic/13110-2002-envoy-electrical-issues-related-to-liftgate/#entry424937

I know, just don't call you Shirley (that's an old movie reference for you Millennials).

 

[IllogicTC]

Well, P0305 is actually rather specific -- a P0300 would be a "general misfire" where it was in the process of, or could not determine, which cylinder it originated from. A 305 makes me wonder if that coil or plug is failing due to the famous water leak. Uncommon problem but it has cropped up more than once around here, and even has a TSB related to it.

Pretty much, since the hood doesn't have a seal along the back edge, rain and whatnot will go down onto the intake resonator, then take the path gravity gives, straight down where it'll collect in the valve cover area usually on or in the wells for cylinder 4 and/or 5. This likely has nothing to do with the communications issue, as this is just between the PCM and the coils. Switch coil 5 for coil 2 or something and see if the code follows the swap (P0302 in this case).

The LGM you pulled should be just fine, by the way. Matching part numbers and previously used (and therefore programmed).

As for the blue wire you mentioned in the OP... regular blue, or light blue? If it was the light blue, that's the comm wire, and with the vehicle running or modules at least actively communicating, I suppose wildly fluctuating voltages could be expected. You may try checking that wire for a ground fault, it happens a lot.

 

[02Envoy02]

Well, P0305 is actually rather specific -- a P0300 would be a "general misfire" where it was in the process of, or could not determine, which cylinder it originated from. A 305 makes me wonder if that coil or plug is failing due to the famous water leak. Uncommon problem but it has cropped up more than once around here, and even has a TSB related to it.

Pretty much, since the hood doesn't have a seal along the back edge, rain and whatnot will go down onto the intake resonator, then take the path gravity gives, straight down where it'll collect in the valve cover area usually on or in the wells for cylinder 4 and/or 5. This likely has nothing to do with the communications issue, as this is just between the PCM and the coils. Switch coil 5 for coil 2 or something and see if the code follows the swap (P0302 in this case).

The LGM you pulled should be just fine, by the way. Matching part numbers and previously used (and therefore programmed).

As for the blue wire you mentioned in the OP... regular blue, or light blue? If it was the light blue, that's the comm wire, and with the vehicle running or modules at least actively communicating, I suppose wildly fluctuating voltages could be expected. You may try checking that wire for a ground fault, it happens a lot.

I gotta tell you, IllogicTC, I don't believe it's a coincidence this erratic idle, rough running, engine light came on, and P0305 code all started right after I disconnected battery.

Maybe the LGM should be fine but something isn't working. Still no rear wiper/washer, keyless entry, or RAP.

I've done a bunch of testing on the wires as noted in previous posts. What, specifically, could I do now?

 

[Mounce]

Test for continuity on each of the wires. Any fluctuation would tell you the wire is bad.

 

[02Envoy02]

Test for continuity on each of the wires. Any fluctuation would tell you the wire is bad.

Been there, done that.

 

[coolasice]

Test for continuity on each of the wires. Any fluctuation would tell you the wire is bad.

+1 especially the blue wire. Until continuity is checked on ALL wires you cannot rule out a broken wire problem.. no connection on blue wire = no liftgate module communications which will result in the exact symptoms you have. If all wires check out then the LGM is most likely the culprit.


http://gmtnation.com/forums/topic/8114-liftgate-control-module/page-2#entry216437