pdesimone48

2007 Trailblazer LT with 145K mi - A week or so ago I got a Liftgate or Rear Hatch Ajar message (I can't remember which), so I went back and slammed it a few times but it still thinks it's open so it keeps my cabin lights on, my rear wiper doesn't work the hatch lock doesn't work and my key fob doesn't work either. Probably because it still thinks it's ajar. I took the plastic cover off and was looking for some sort of sensor switch stuck but there is none that I can find. I tried switching out the lock and it still doesn't work. I checked the wires at the top of the liftgate but couldn't see any apparent breaks.
Does anyone have anything else to check?
Does anyone have a wiring check procedure or something they want to share?
Where is the liftgate module and how do I check to see if it's functioning?
What's this Body Control Module, where is it and how do I check it's functionality?
Any help would be greatly appreciated.
Oh yeah, once I fix this I need to dive into the annoying Service Tire Monitor problem.
Thanks
Phil

Trailblazrr07

Ok well I don't know if anyone had replied to you but.. Their is a harness that comes out of the body into the tail gate at the top left in a rubber boot.. You need to pull the boot out and inspect the wiring inside for frade or broken wires... You need to look at the black, or orange wire witch is the signal wire for the tail gate module... If everything is good their you have to look under the headliner their is that harness under their... Check to see if the plate light is working also... If not replace the bolbs the are connected to the same harness and will cause issues in the gate... Also look for corrosion inside the bulb sockets.. Good luck

pdesimone48

I changed out the LGM with a used supposedly working one and I got nothing. I also changed out the lock mechanism itself and nothing. I put the originals back on. I did check the wires coming out of the boot at the top of the liftgate and saw nothing broken. I have to go back and test for breaks inside the plastic shielding. I'll use a meter or a test light and a needle to check. Anyway I just went out and checked and my license plate lights are both out. So, tomorrow, I'll get two new bulbs and check the wires coming in for power. If you have any wiring diagrams or pictures with an explanation of what wires are hot and ground or anything else, that would help. I'll attach some pictures of what wires I'm dealing with in the mean time. Thanks for the tips. Phil

Trailblazrr07

Ok I see the LGR and yes sometimes you will get a bad used one... Sometimes a intense inspection of the harness inside the boot on the left top of the tailgate and the body will find problem... Yes the tail light bulbs will cause the problem cause it is all continuous current to talk to the othe mods... When you pull the bulbs look inside the sockets to see if their is any corrosion inside them... Yes use a test light to see if you are getting power to them... If not look at the fuse under rear driver side seat to see if you have power going in and out of the panel...it will be #3 lower right corner 30 amp.. If so then the next step is to look at the harness up under the head liner rear of the truck where the harness goes through the body to the tailgate... That's where my problem yes it will be a pain to get out but it what will you will have to do ...like I said if the fuse is good both sides of it the you will have to chase it Dow from the fuse box to all mods... If one goes none will be able to comunicate to each other... And sorry no I have no diagrams... I do avionics so I just chase it down or look on line for any place I can find a diagram for what I can't seem to figure out... Let me know how it goes maybe I can point you in another direction to look for the problem...but it is in that harness for the tailgate... Or tail light bulbs.. Good luck

Trailblazrr07

You will be looking at the black and orange wires .. Black ground and orange is commuication to mod... You can also hook up a ground to the little hook in the back behind the rear seat to the black going into the LGM to see if it is a bad ground..but don't leave it like that it will cause more problems... But at least you will know if it is the ground or communication wire

pdesimone48

Roger all of that. I will try as soon as I can. It's snowing in NJ today so, it will have to wait until it clears a little. Oh and thanks for pointing me to the license plate being out. I didn't realize that and don't really want to get pulled over for having it out. That's a good excuse to pull you over.
Thanks

pdesimone48

Well, I had partial success with your license plate bulb tip.
Both bulbs were out so I replaced them. As soon as I put one bulb in I herd the locks start to click. When I put the second bulb in I herd louder things happening. So, I tried my key fob and yee haw my locks worked. That said, when the lift gate is open the actual lock mechanism makes a shushing sound about every 5 seconds like it's trying to lock the lock. Also, the license plate bulbs don't light up and my rear wiper still doesn't work. Arrrrg. So, at least my locks are working using my key Fob. So, what do I check next? I'm getting 12 volts to the connector to the bulbs but when I probe inside the bulb socket I get something like 2.5 volts, weird. Anyway, I appreciate the help, any other suggestions will also be greatly appreciated.
Thanks

Trailblazrr07

Well you still have a ground problem somewhere in that harness... Sorry but it's in their somewhere...did you check the fuse...??? Make sure have power on both sides of it... If you do the it's in the tailgate harness somewhere... Like I said you can try jumping the ground to somewhere on the truck just make sure it's clean metal...your best bet would be in the harness coming out of the body to the tailgate... That way you will have all miss in the gate grounded...

Trailblazrr07

I hate spell correct... Lol I meant to say mods in the tailgate

pdesimone48

Well, I went back and took your advice to bring a ground back from the rear seat fuse box. Checking the connector coming out of the boot at the top of the lift gate I noticed I had 12 volts coming from the orange wires using the good ground. So, I touched the ground probe to the black connector wire and got almost nothing to nothing. Bingo, it must be the ground from the connector back to the fuse box. Long story short, I was looking at how to take the headliner down when I decided to slice the boot from the bottom to get better access and when I did two wires, one orange and one black came sticking up completely severed. I was like YES, that's exactly what I wanted to see. The orange wire must have been hanging by a thread and the black must have been completely severed. Some solder and some electrical tape and I was good to go. Everything worked again. My Rear wipers, my license plate light, my key fob and my interior lights shut off. My tire monitor even has numbers showing instead of dashes. I'm attaching a picture of the wires.

Anyway Trailblazrr07, thanks for the help. It really helped me zero in on the problem.

So, now, how do I mark this SOLVED?