Intermittent Serial Data Problem

[BigDogYJ]

Can you tell me how to access the ground in the dash you're talking about? Remove the top dash cover?

I seem to remember accessing the upper ground by removing the a pillar trim from the driver side and it was accessible straight down near the base of the windshield. Im not 100% on that, might need to pull the upper dash cover out a bit. but something tells me it's accessible right in that opening. or it may have been accessible from removing the cluster and reach through an opening in the cavity behind the cluster. let me see if I got pics of it when we were working on it.

 

[BigDogYJ]

Can you tell me how to access the ground in the dash you're talking about? Remove the top dash cover?

looks like it was accessible with a swivel and some extensions through the gap after removing the a pillar trim. then we could look through the windshield and see the ground post.

 

[S33k3r]

I finally fished the two splice packs out under the dash to try to isolate the problem while there was a loss of communication. However, removing the comb from either one of them had no affect. I expected data to return to the cluster as soon as I unplugged it. I suspect a bad ground. Hard acceleration and bumps seem to cause data to flow or be interrupted. Also, one time I had the back hatch open and I threw my tool bag in there and the lights came on like it caused the data to return. I need to find grounds and modules in the back to check.

My engine has a knock sensor code and the oil pressure sensor seems to be not working, so as soon as I can get a set of knock sensors I'll pull the intake and swap those. While I'm in there I'll replace the valley cover gasket, Intake manifold gaskets, valve cover gaskets, oil pressure sensor and check and clean or repair the two grounds on the back of the block.

Be careful with that knock sensor code. We kept getting that even after we replaced the knock sensors. The wiring in there is annoying -- we had ours replaced -- and make sure you use Delco knock sensors. They originally used an off brand and then "hilarity" ensued. They replaced the knock sensors -- again! -- with Delcos, and did not charge us for it. We've not had issues since.

 

[axekick]

Thank you BigDogYJ. That's very helpful. fixing that up is next on my list.

As far as the knock sensors, I did go ahead and spend the extra on the ACDelco sensors. I'm not too worried about that job, though. I can get the intake off in 10 minutes. I've learned that just moving stuff out of the way is easier than trying to fit my hands where I can't see. Basically doing things the hard way is the easy way, so I have a lot of practice removing intakes on trucks. Now I just need to get quick at removing the dash. It doesn't look that hard, except that I have the full center console so I think that makes it harder.

The truck is at the exhaust shop now getting a normal sounding muffler on it. It had a noisy flomaster dumped under the truck. I'll get to work on it a little throughout next week. I'll update if I make any progress. Thanks everyone for the help and advice so far.

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[axekick]

I got my knock sensors and oil pressure sensor in. I cleaned up the two grounds on the back of the block, cleaned my valley cover and valve covers real good and got it all back together. The rear knock sensor was full of water. It looked like it had been full of water for 10 years. I had to basically break it apart to get it out. I did seal the new sensors in. The knock sensor codes are gone and my oil pressure is reading now. I had to do it twice because I did it in the dark and I put the valley cover gasket on upside down so it was leaking a lot of oil down the back of the motor. No biggie. I fixed it over my lunch break the second time around.

I still lose class 2 data, but not as often. I think the warmer weather makes it better. Here's a clue, though. I can tell if there is communication or not because of the dome lights. I noticed the lights came back on one time when I closed the rear hatch. Then, another time I was standing in the back with the hatch open and the com was broken I just bumped the driver side rear wheel well and it came back. I still haven't started pulling off trim to see the wiring harness but I suspect it's in the back. However, I had the rear hatch harness disconnected when that happened so I am sure it's not in the hatch. Maybe it'll be the rear AC module. The rear AC doesn't work right now.

 

[S33k3r]

We had an issue with my daughter's 2005 Suburban 1500 that sounds similar. There is some kind of wiring or even a junction of sorts behind the C pillar on the passenger side. We had wires that had rubbed raw and snapped. So you might start your wire chasing there.

 

[axekick]

I pulled the trim out of the drivers side rear and found the harness back there. I didn't see any broken or exposed wire, but I didn't remove all the tape. It has been accessed before. I can tell because the harness wasn't taped to the plastic clips in most places. I moved it around and attached it back to the clips and put the trim back. I also cleaned and tightened a couple grounds on the rear driver side frame. I drove it around for a while and it never lost communication. I'll drive it all week after today and see how it does. If it doesn't happen in a few days, I'm going to buy a cam and lifters to address the lifter tick it has. My next project on it is getting the AC working. I'll start a new thread for that.