Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner

1 - 12 of 12 Posts

·
Registered
2005 gmc envoy_denali_xl
Joined
·
10 Posts
Discussion Starter #1
Trailvoy fans. Please help. I posted earlier and have more information now. I have a problem with my reverse lights not coming on.

I checked both fuses with an Ohm Meter (one up front #27 and one under left passenger seat #32) and both are fine.

While in reverse (and also neutral) with the engine running, I measured 13.1 Volts on both sides of each fuse. This should also indicate that the fuses are OK. This is odd also as I would have thought that the power go off on one of these fuses when the car is in neutral.

I tested each light bulb with an external 12VDC source and they are both OK.

When moving between neutral and reverse, the BCM (Body Control Module) has a clicking noise like there is a relay inside. This tells me the BCM is getting the signal to turn on the reverse lights.

What can I test next to solve this problem? Is there a schematic or wiring diagram for this part of the electrical system available?

I cant imagine any cause and effect but I recently replaced the air shocks and rear brakes. I did not notice if the problem started at that time. This is the only service in the back of the car in recent memory.

Here are some photos I took of both fuse boxes and where I am measuring.



Your help would be greatly appreciated.



 

·
Registered
2002 chevy trailblazer_ls
Joined
·
257 Posts
Have you checked for corrosion in the bulb sockets? Maybe bend the wires on the bulbs so there is better contact. I have had to do that with my break light bulbs, and I also use dielectric grease as there was some corrosion in the socket that I was able to scrap and sand off. Haven't had a problem on them after the bending and dielectric grease.
 

·
Registered
2005 gmc envoy_denali_xl
Joined
·
10 Posts
Discussion Starter #3
Thanks Strom for the suggestion

I just went out to check on the sockets and they seem clean, tight and corrosion free. I added the dielectric grease too. This is a great suggestion.

Still no backup Lights.:(
 

·
Registered
2002 chevy trailblazer_ls
Joined
·
257 Posts
I had to use an exacto knife to pull the wire a little out a little further to really be sure it contacted the sockets. The bulbs I had, the wire actually melted a little into the base. Thinking about it it could also be a problem in circuit board, if you want to call it that. Trying to find a pic of what it looks like in the inside. It is just metal strips going to each socket basically. Sometimes vibrations could weaken them and either break or come off the melted plastic rivets and short out against eachother... There were recalls on early models, but can't remember what year it cut off. But newer ones have been known to go out too.
 

·
Registered
2005 gmc envoy_denali_xl
Joined
·
10 Posts
Discussion Starter #5
Still working on it...

OK. I pulled the reverse bulbs out and measured the ohms on both of the pins of the socket and one is definitely connected to ground. The other has no voltage.

I want to remove the fuse block and BCM to check the voltage at the connectors there. I am having trouble figuring out how to remove it all. Does anyone have a clue? Do I need to remove the seat to access it all?

Here is a schematic of the circuit.

http://db.tt/5avuIBHx

Here is a photo of the Rear Fuse block. (Fuse for reverse is out)

 

·
Registered
2005 gmc envoy_denali_xl
Joined
·
10 Posts
Discussion Starter #7
What's in between the fuse and the socket for the bulb?

I have power at the fuse and no power at the light bulb sockets. What can I measure in between?
 

·
Registered
2005 gmc envoy_denali_xl
Joined
·
10 Posts
Discussion Starter #9
Still Checking...

OK. As you can tell, I am a big fan of photos. I opened the rear tail lights and the reverse light wiring does not appear to run there. Or does it? I follow it to the frame and then it heads to the from of the car and disappears under the rear seat.

I took off the left passenger seat to show what the rear fuse block looks like and also expose the BCM.

Does anyone know what terminals to test on the BCM?







 

·
Registered
2005 gmc envoy_denali_xl
Joined
·
10 Posts
Discussion Starter #11 (Edited)
Reverse Lights Failed Again.

Last year I sent in a request to y’all for information to help with my reverse lights. Well… I ended up taking it to the dealer and they got them working. What was it? They told me the fuse was bad. $ 225.00 to replace a fuse. I don’t believe this was the issue as I checked all fuses front and under the rear seat. And the invoice did not list a fuse on it but just labor. I would think a dealer would account for even a fuse. I suspect the BCM was the issue. It has happened again. Now what? I feel insulted taking it to a dealer to get reamed for a fuse. Here is the fuse I checked.

https://docs.google.com/file/d/0B3IWkJXng4KMelpYNmJhdEJGVmM/edit
 

·
Registered
2008 chevy trailblazer_lt
Joined
·
300 Posts
Its a pretty old thread. You might want to start again by testing for voltage at the bulbs when you are in reverse... don't get run over... :)

As you probably know, there are only two wires going to the reverse bulbs, one is grounded and the other is powered which comes in a "round about way" from the BCM. So the test would be to see if the bulbs are seeing voltage. If not move to the BCM to see if it is getting out. Then you can go from there.
 
1 - 12 of 12 Posts
Top