I broke it somehow. Clunk-SNAP and 4x4 went dead.

Sparky

Original poster
Member
Dec 4, 2011
12,927
I made a quick sharp left turn onto my road on my way home from work because of traffic. As I did so, I heard a thunk-SNAP noise from the truck. I had the windows down and it sounded like it came from the front, possibly driver side, but I can't say for sure. The truck didn't lurch, skip, or anything else weird, just made the turn like it normally would. When I looked around I noticed my 4x4 selector switch was dead. To be honest I don't know if it was lit up right before the sound or not. I'm 99% sure it was lit up when I left work.

I parked the truck, which involves backing and turning a tight radius and it behaved normally (no funny noises or crow hopping). Shut the truck off, waited, turned it back on, and the "Service 4x4" light came on for a second, then shut off like normal, but the selector switch was still dark. Flipped through the modes and the actuators were silent. Shut off the truck, pulled the 4x4 fuse from the rear block, waited, put it back in, and checked again. Same thing. No idiot light, no selector switch.

I glanced underneath to see if anything at least looked weird but all appears fine from a cursory glance. It started raining so I haven't been able to actually jack it up and crawl underneath to check stuff out, but I wanted to probe the greater minds here for ideas.

Up until now I've had no problems with the 4x4 except last year when I broke the disconnect housing trying to service it. It's been fine since. I do have a few spare disconnect parts stashed away in case I need something there.

It just seems weird that the "service 4x4" light isn't lit up with the system obviously non-functional :confused:
 

Voymom

Member
Feb 3, 2012
2,523
Sparky said:
I made a quick sharp left turn onto my road on my way home from work because of traffic. As I did so, I heard a thunk-SNAP noise from the truck. I had the windows down and it sounded like it came from the front, possibly driver side, but I can't say for sure. The truck didn't lurch, skip, or anything else weird, just made the turn like it normally would. When I looked around I noticed my 4x4 selector switch was dead. To be honest I don't know if it was lit up right before the sound or not. I'm 99% sure it was lit up when I left work.

I parked the truck, which involves backing and turning a tight radius and it behaved normally (no funny noises or crow hopping). Shut the truck off, waited, turned it back on, and the "Service 4x4" light came on for a second, then shut off like normal, but the selector switch was still dark. Flipped through the modes and the actuators were silent. Shut off the truck, pulled the 4x4 fuse from the rear block, waited, put it back in, and checked again. Same thing. No idiot light, no selector switch.

I glanced underneath to see if anything at least looked weird but all appears fine from a cursory glance. It started raining so I haven't been able to actually jack it up and crawl underneath to check stuff out, but I wanted to probe the greater minds here for ideas.

Up until now I've had no problems with the 4x4 except last year when I broke the disconnect housing trying to service it. It's been fine since. I do have a few spare disconnect parts stashed away in case I need something there.

It just seems weird that the "service 4x4" light isn't lit up with the system obviously non-functional :confused:

My Envoy did this over winter, My hubby fixed it by playing with the wires under the steering wheel lol Our selector light came back on and 4x4 worked fine. May not be the same situation, but maybe a possibility?
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Clunking noises could not kill the lights on the switch. But a cut harness could have blown a fuse. Do you have a meter and the schematics?
 

Sparky

Original poster
Member
Dec 4, 2011
12,927
I know, which is why I'm second guessing when the lights went out on the switch. Fuses in the fuse boxes are good, I tested them. I have a Haynes manual which has schematics in it, and I have a DMM. I'm going to have to crawl under there and check everything out and I would have except for it started raining.

Maybe the TB is acting up because it is jealous of my new toy. First the head unit harness adapter goes bad on me, now this lol :crazy:
 

Sparky

Original poster
Member
Dec 4, 2011
12,927
I did some searching here and on Trailvoy as I started doubting myself as to whether I checked the right fuse or not. Sure enough, I hadn't. Dummy.

Fuse #8 under the hood is labeled ATC and that is the fuse I wanted. I was looking for one that said 4x4 or TCCM and didn't know what ATC meant. Well duh, ATC = Automatic Transfer Case :duh:

I pulled #8, checked it out, put it back, and hit the ignition. All the lights on my 4x4 selector switch lit up (yay!), then all went out and the "service 4x4" idiot light stayed on (boo). Shut it off, turned it back on, same thing. From what I've read on here and on the old site, this is a classic sign of a crapped out 2002 TCCM, correct? I guess I got a good run out of mine, 158k miles and 10 years, not bad for a known bad part :biggrin:

I'll be ordering a "new" (used) replacement soon. I've seen a few different part numbers of TCCMs floating around on ebay, are there any that I should stay away from or ones that are more ideal to get? I'm seeing 15085386, 12584313, 12580060, 12590220, etc etc... Looks like 12588290 is 2002's part # so I'll avoid that one. Also is there any difference from 03-05 and 06-09 on the TCCMs or are they all interchangeable?

This also convinces me the snap sound I heard was totally unrelated and probably just a larger stick or something I ran over in the road. All it did was make me look around and notice the switch wasn't lit up.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Sparky said:
...this is a classic sign of a crapped out 2002 TCCM, correct?...
You got it in one. :thumbsup:

As far as I know, they're all the same as long as they have been programmed for a 4WD, not an AWD, vehicle. There's some minor variation for gear ratio, but that just sets the algorithm for A4WD engagement speeds, and anybody who's been reading my advice will know I'm death on using the A4WD mode.
 

Sparky

Original poster
Member
Dec 4, 2011
12,927
There is one on ebay from an 04 Envoy for a decent price so I'll grab that. I'm not worried about the A4WD, I used it once and never again :crazy:
 

jbones

Member
Dec 5, 2011
658
Sparky said:
I do have a few spare disconnect parts stashed away in case I need something there.

Glad you figured it out because all I could figure was that you “stashed” one of them spare parts in the wrong place. :wink:
 

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