New Electrical issues

[amrg]

Im having what seems to be an electrical issue that basically got my truck disabled. Truck will start no issues, but within a few seconds the traction lights/stabylisys will come on, the ABS, check engine, passlock and battery light. The dials are either not reading, or start not reading (the fuel gauge goes down to empty)
Moving the trans from P to drive to neutral/reverse doesnt register immediatly on the IP and the reverse camera doesnt come up.
I checked for lose cables, battery terminals are aftermarket and tight like hell. Battrry and alternator checked out but I swapped them with perfectly working ones and same exact issues. Pcm connectors are perfectly seated, mega fuse at the fuse box is good and I checked my 2 ground cables (battery to body and battery to engine) and they are solid. For some reason, when I try to read the codes with the obd2 scanner and torque app, the truck goes into limp modes (engine whines and runs crap), but reading the codes using an advanced code reader doesnt do that. Eitherway, no codes are coming up and if they do (rarity) they are generic codes that point to nothing.
You can see the whole thing here...

https://youtu.be/LKePBZ792Uw


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[Bowser-II]

Do your various lamps (headlights, overhead lamps etc) work and you can control them on/off?

Do you have any aftermarket wiring installed and can you temporarily disconnect it?

Have you had any water saturation recently, even localized to part of the truck?


This will help tell you if it is a computer BCM or accessories issue or more localized and/or related to a specific harness.

Then I would start making sure the wiring connectors from the battery to the fuse box then to the BCM and then to instrument cluster are good.

This will allow you to tell if it localized to mostly the gauge cluster (actually had some issues like this before and it was replaced under warranty).

I would also verify the wiring and connectors at the fuel pump next.

I have had issues with fuel pump wiring for years and still can’t trace it all down.


Start with that let’s see what happens


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[Happy Hummer]

It is def time to start scoping, scanning and using a test light.
I would personally start a to do list:

1>I'd back prob the CTS and verify it had good ohms reading and when feeding to and from PCM that I was getting correct values.
2>I'd check each ABS tone ring/sensor output/input and ohm reading.
3>I'd verify that my encoder motor was functioning. Pull it from its housing and go through each of the settings noting movement or lack there of.
4>I'd personally verify that it is NOT the gauge cluster, ignition assemblies.

Schematics and values are going to be very important moving forward.

 

[4speedfunk]

I did a SAS on a customer’s H3T a few years ago and it was doing the same thing. He warned me ahead of time about the issue...not related to anything I did. It would go into limp mode and I would have to pull over, put the trans into park, then back into drive, and take off again. Five miles or fifty miles later it would do it again.

He had previously installed twin batteries and an automatic coupler switch. My initial thought was this may be the culprit so I removed that and hooked up a single battery like stock. It still did the limp mode thing. I tried everything with no success. I eventually gave up and he picked the truck up and took it home.

A year or so later he finally figured it out. The PCM or BCM (not sure which) was bad. Rain had gotten down into the kick panel and soaked the computers. There was a bunch of corrosion on the connectors and inside the case of the computer. This is not cheap but, he replaced it and the problem has never returned. Not sure the source of the water...I assume it was clogged sunroof drains. Might try swapping in a different computer.

 

[amrg]

Thanks for the input guys! Im now looking for someone who is willing to touch it... My electrical experience is minimal (im more into mechanical) and if the wire isnt visibly shorted I dont know how to start. It doesnt help that every mechanic Im going to isnt willing to work on it either! Since its 120* outside, its not the best time to start learning either!
I did open up the kickpanel and check the connectors at the bcm, got one unplugged and looked clean. The weather here is dry so apart from washing the truck no water gets on it (and I did open up the drain hoses last November to unclog them as water was getting trapped in the sunroof drain and spilling on my head when it did rain that time)

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[Happy Hummer]

I'm in NO way trying to push as you tube channel...but south main auto is where I would start. This guy fixes alot of stuff others walk away from. I believe he is located somewhere up state NYC. His videos are very good and he covers a ton of chit!

 

[alrock]

I'm in NO way trying to push as you tube channel...but south main auto is where I would start. This guy fixes alot of stuff others walk away from. I believe he is located somewhere up state NYC. His videos are very good and he covers a ton of chit!

Push, push! YouTube can be a good source of info.

 

[amrg]

Thanks for the info guys... I wanted to update this thread, I had my truck sent to a shop to do the work (not too confident with electricals) and they worked on it for a few days. Turned out to be a few chaffed wires between the fuse box and pcm that needed to be fixed. They said they were getting improper voltage readings on those so they replaced them. Now its running properly as it was before the issue.

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[Guerrero]

Thanks for the info guys... I wanted to update this thread, I had my truck sent to a shop to do the work (not too confident with electricals) and they worked on it for a few days. Turned out to be a few chaffed wires between the fuse box and pcm that needed to be fixed. They said they were getting improper voltage readings on those so they replaced them. Now its running properly as it was before the issue.

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Glad that you finally found it!

Those kind of symptons are usually to a bad ground, bad wires (some short like yours) or a bad Pcm, Tcm or Bcm module...

Please post a picture or a indication of where those wires are located....that would be a huge help in case somebody with an H3 experiences the same! (Usually all cars of a certain brand and model fail in the same way)

 

[amrg]

Sadly i dont know exactly where it was since I didnt work on it myself. But according to the tech, the state of my wiring is the worst hes seen in 15 yrs work and he saw much older cars with wiring in a much better state! I can probably blame the fact the H3 engine bay is a heat trap that doesnt let hot air out easily and I will consider making my hood louvers functional to help the engine bay stay cooler (for the sake of the wiring).
On my other H3, 2006, the other day I noticed a hole in the coolant overflow tank, all it took was for me to touch it for it to get bigger. The plastic is in such terrible state its barely holding together!

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