Truck electrical issues IDEAS WELCOME
 

So here's the story. 08 gmc 2500hd 4x4 crew cab long box. Last friday my wife was driving into town and the tranny kicked into limp mode. She pulled over and shut it down, and the truck would not start again. When I got there we noticed the indicator line that tells you what position the gear shifter is in wasn't there. Tried everything I could but could not start the truck. Got it towed to the mechanic. When he looked at it on Monday it still didn't have the indicator line but after turning the key 20 or more times the line appeared and the truck started but the whole left side of the dash board wasn't working properly( needles jumping all over ) then after a few seconds the line disappeared again and kicked the tranny back into limp mode. After a week of tracing possible problems we can't find anything. Now it's been 3 days since we have been able to start it. It won't even start by powering up the starter. The mechanic is stumped I'm stumped. Just looking for possible ideas to try and hoped someone on here had a outside the box idea we could try.


We have replaced the switch on the ignition
Checked all fuse boxes for good connections
Traced all wiring we can find from the steering column
Checked all the grounds

No one has been able to find where that indicator line is powered from yet???


Thanks for any ideas, even simple ones, never know something might just work

Take Off the braided flat aluminum ground from motor to body
 

Just went through Dodge Diesel Hell with an 03. All it ever was is that flat braid ground strap from the back of the engine to the truck body. Was very white, so it looked normal. But is aluminum corrosion.

Either paint the sucker with CLR, or take it off and soak it in CLR and CLR the places that the bolts go through.

The Tranny is isolated to the engine and relies on the engine ground strap. Engine sits on rubber snubbers so never is grounded to the frame otherwise.

Same thing for the Tranny and its rubber mounts.

Cost you $8 to find out. If it works, I like Kokanee 15 packs. We can get together and cry in our beer about our Trucks.

Drewski

I’d be suspicious that your instrument cluster itself is at fault.

Network down? What happens when he checks the network.

Had that problem on a 08 gmc work truck. Shifter linkage was worn enough that it wouldn’t always go all the way into gear. Truck started throwing all sorts of fits when you hit a bump or went through mud.

Shifter linkage was replaced last winter. Even turning the lever on tranny by hand changes nothing

The scanner won't connect for some reason either so can't even see if it's kicking a code

Thanks for all the replies. No idea is worth not checking at this point

Sounds like a ground issue to me. I'd remove and clean all grounds and mounts.

My friends 07 shut down in similar fashion. Drove up to his cabin, next morning would not start. Towed to dealer. Dealer said it was a solenoid in the transmission failed. Designed to kill power to the engine from starting to stop damage from happening by driving it.

Would this also explain the dash issue? Or could it 've two separate issues?

This is a man who knows. Grounds are really important on modern vehicles.
Buddies 2009 Avalanche similar situation was the grounds. His started by flashing the lights and door locks cycling.

Scanner won't connect. So that means you can't communicate with any modules?Sounds like a network problem. Should be able to communicate with some of the modules .

If someone had told me to use $8 worth of CLR before spending $1,400 on mechanics, I would have tried the cheap and fast route. But that's just me, in hindsight.

Drewski

Under the drivers door there is a body mount there should be 2 ground wires there . Clean the contact surface and use a proper bolt and nut to reattach. Get rid of the screw . And at the back in the left rear frame withe all the wires i the loom . There is a resistor for data bus lines. Its used to terminate the bus system. There is a updated plug in cap (old resistor fails and truck no run)

Saw a youtube vid last week about a phantom electrical problem in an older Benz.

Turns out there was a fuse-box in the edge of the dash right beside the driver's window, which had most of the fuse contacts corroded. (Probably from leaving the window open during a rainstorm overnight.)

The corrosion was bad enough that the can-bus (or whatever it was) although having some electrical connectivity couldn't maintain a proper signal to any processing modules.

I'd check any and all points of potential conductor contact corrosion.

Is the anti theft light flashing as well?
If so pm me my father inlaws truck same problem
I drove all the way north east of red earth to trailer it to a gm dealer to fix

My truck doesn't have anti theft as far as I know.

Had a look at my 03 and couldn’t see this braided strap, any more details on where it’s located? Passengers or drivers side?

Thanks!

That doesn’t help my question, hopefully it helps the OP. I was asking Drewski about his 03 Dodge.

Sorry for the hijack.

All gm trucks since 1999 have anti theft
It is a small red light in dash
Cant quite remember if it looks like a lightning bot or something different when you turn your key on

I don't recall him saying he had a issue in the dash.

Nsbu switch

One of the most common problems with the Allison transmission is failure of the Neutral Safety Back Up switch. Some of the symptoms of failure include but are not limited to: No start condition. Gear shift indicator on dash not following properly.

“CHECK ALL YOUR GROUNDS” I’ve even found loose battery cables on units. Just last week has a unit in where it was a no start and you couldn’t communicate to the ECM and all it was was a loose cable on the battery.

My 2013 had a wire short out above the fuel tank. Did all kinds of weird stuff. Gauges going wonky and limp mode.

"Redundant ground wires"
 

All vehicles have redundant grounds. There should be one or more to the steel dash panel as well as to the steering column. Poor ground conditions can cause problems you wouldn't even think were possible.
Also, did you disconnect and reconnect the battery? This should (temporarily) reset a condition that would put the engine in limp-mode. My '03 Avalanche went to limp-mode when the "fly by wire" throttle body failed.

Worth a try
 

Not sure if you've checked all electrical connectors. There is one to the tranny in a rubber grommet that can create issues if it doesn't have a great connection.

Body computer can act up if you have any LED's anywhere in your system. Creates some messed up issues, took me 2 years to figure out. Connects in to the TCM and ECM and creates voltage spikes.

Also check for corrosion on the under hood fuse box (just pulls out of the truck). Check the underside of the box for any obvious signs.

Also check out gm trucks and silveradosierra sites for some more help.