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TBI throwing code 42

I would not consider that ground clean. To me, clean would’ve bare shiny metal, star washer, and bolt. Maybe it just doesn’t come through in the pic. :dunno:

And I can clearly see what your main issue is in the 3rd pic … “Made in Canada” :rotfl:
 
Yes, GM "sealed" some of the grounds with that stuff. Best to leave it alone, but since you already hit it, you need to get the body to bare metal there (yuck) and then slather everything with dielectric grease or it will corrode and fail to ground at some point.

I assume the rust is due to the cap terminals rusting from sitting, and the rotor knocking it off as it rotates. Terminals used to be brass to not have that issue.
 
green55 said:
Crap I wish I hadn’t touched that ground.
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I think all the crud you cleaned off of the ground is a spray on undercoating/ sealer that was sprayed all the way around your air box and heater assembly. I cleaned mine off recently, and it didn't make a difference. added a second ground strap because I had one laying around. probably was not needed. light coating of dielectric grease on both of them
 
Just to provide some resolution on this for the next guy:
I gave up and sent it to a shop. They tracked down the issue. One of the wiring harnesses connecting to the ECM had water damage -- must've been a leak at some point during it sitting for years because there's no evidence that its leaking now. Harness got fixed, but ECM was still having issues, we think it was damaged because of the poor connection. Everything is good with fixed harness and new ECM.

Thanks as always for the help y'all. Bummer I couldn't figure this one out but glad that its back on the road!
 
interesting. appreciate you following up!

wonder what part of connector on the harness could be damaged by water unless there was severe corrosion or arcing happening?
 
Corrosion/build up of that nice crusty green stuff that can pop up when water exposure happens. I think that prevented it from getting a good connection. My understanding is that they really didn't repair any actual wire, but the connector itself, which had the corrosion. That's also what it looked like when I took a look behind the glove box.

I asked a bunch of questions because I wanted to a) know what was replaced and b) understand why it happened. That's what I was told. I don't think these guys would BS me, but I guess you never know.
 
green55 said:
Corrosion/build up of that nice crusty green stuff that can pop up when water exposure happens. I think that prevented it from getting a good connection. My understanding is that they really didn't repair any actual wire, but the connector itself, which had the corrosion. That's also what it looked like when I took a look behind the glove box.

I asked a bunch of questions because I wanted to a) know what was replaced and b) understand why it happened. That's what I was told. I don't think these guys would BS me, but I guess you never know.
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your truck go crossing rivers, or mud bogging in the past? or you thinking the windshield gasket was leaking? you blow a heater core recently (ive done that 2wice now)?

My k5 spent about 2.5 years without the shell on... tried my best to tarp and protect from the little bit of rain we get here, but, it got wet several times, and once the carpet and padding is wet, everything steams up under the dash and EVERYWHERE in the truck... ive been worried about that a little. Several times i had to pull the seats and the padding and let it dry in the garage for a month. Blah.
 
Definitely no river crossings or mud bogging that'd be intense enough to cause this. But while it was sitting, a branch fell on the roof/window and broke the window. Not bad enough to go all the way through, but cracked pretty badly. I wouldn't be surprised if that messed with the integrity of the windshield gasket seal. I don't know how long it was like that before I got it, but potentially years. I think that's what allowed water to get in there - I don't think its currently leaking
 
Probably from condensation. If they just cleaned the connector on the harness I’d still be concerned that the corrosion went back inside the wires itself under the insulation and will lead to issues in the future.
 
green55 said:
Definitely no river crossings or mud bogging that'd be intense enough to cause this. But while it was sitting, a branch fell on the roof/window and broke the window. Not bad enough to go all the way through, but cracked pretty badly. I wouldn't be surprised if that messed with the integrity of the windshield gasket seal. I don't know how long it was like that before I got it, but potentially years. I think that's what allowed water to get in there - I don't think its currently leaking
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ahhhh ok. water got in through the broken glass, or the seal... and it prob got the steam treatment for a while


-which is exactly what happened to my truck a few years ago... greaaaat.

good info here though.
 
When checking your grounds, check your resistance from interface to interface if you can. I try for .5 ohm or less. Go from ground strap to the flat surface, do not read off of the bolt since the threads are providing the ground and that can be compromised over time. I had always read off of the bolt until I learned the right way to do it from my new line of work.
 
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