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Loss of Electrical in truck

Tiny
COLLIN LACOBELLI
  • MEMBER
  • 1990 GMC TRUCK
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 232,000 MILES
I have the truck listed above k1500 that has an odd issue where if you turn the steering wheel to a certain position, let’s say 11 o’clock on the wheel, all the power in the truck shuts off and if the truck is running it will also shut the truck off turning off power to the fuel pump and probably everything else to. I have replaced the ignition switch on the column (didn’t work) and I have torn the column down to the point where you have to pull the two pins out of the sides of the column and can’t find any issues yet. Is it possible that the rod that goes from the ignition switch to the key lock cylinder is getting caught up or the rod is broken or bent?
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Sunday, December 8th, 2019 AT 10:43 AM

16 Replies

Tiny
AL514
  • MECHANIC
  • 4,118 POSTS
Hello, have you tried unplugging the power steering pressure switch? When they go bad it can cause stalling and other unwanted symptoms. Try that first there maybe be 2 of them.
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Sunday, December 8th, 2019 AT 11:19 AM
Tiny
COLLIN LACOBELLI
  • MEMBER
  • 11 POSTS
I do not believe my truck has a power steering pressure switch. I don’t believe they added that until 1995 in the GM trucks.
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Sunday, December 8th, 2019 AT 3:29 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,942 POSTS
Have you checked the positive and negative battery cables? It sounds like you have a bad connection at one of them. I would try replacing the positive cable I have seen many strange things happens because of it.
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Monday, December 9th, 2019 AT 11:42 AM
Tiny
COLLIN LACOBELLI
  • MEMBER
  • 11 POSTS
I have checked them before but I’ll give it another shot. Thanks
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Monday, December 9th, 2019 AT 2:11 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,942 POSTS
It like the steering wheel column is moving something causing the problem. Can you move the wiring harnesses around the colum to see if you can get the same thing to happen?
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Tuesday, December 10th, 2019 AT 12:07 PM
Tiny
COLLIN LACOBELLI
  • MEMBER
  • 11 POSTS
I can’t seem to get the same result by wiggling any wires. I’ve even tried unplugging fuses to different circuits that run to the column to see if the problem would still occur if they didn’t have power and I still have the same problem. Is there any circuits on these trucks that actuate during turning? Just because it’s weird how the ignition switch had one burnt up contact but still was working, it could be nothing but just wondering.
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Thursday, December 12th, 2019 AT 3:24 PM
Tiny
AL514
  • MECHANIC
  • 4,118 POSTS
Do you have a test light? You should check fuses while the issue is happening and see which circuit is losing power, it sounds like the ecm is losing a power or ground. If you can identify which fuses are going dead we can isolate the problem circuits better.
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Friday, December 13th, 2019 AT 8:47 AM
Tiny
HMAC300
  • MECHANIC
  • 113 POSTS
This is what I would do: check the ignition harness first on steering column to see if any wires have worn the insulation off and cause the problem then check harness going to ECM as it may have worn through and hit the frame. If I remember correctly the ECM sits below battery and harness can rub on frame or worse yet battery acid has eaten through harness and is causing problem because frame may be moving a bit due to age of truck as well as sharp turns in the offending direction.
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Friday, December 13th, 2019 AT 9:32 AM
Tiny
94 TRANSAM
  • MECHANIC
  • 680 POSTS
My 2 cent would be there is a PCM ground bolted to the dash frame below the steering column. That ground is dependent on the frame being bolted to the body. I suppose its possible that the torsion on the column in just the right place may be moving the dash frame to a place where its losing ground to the body. I would check the ground below the column and re torque all the dash frame bolts.
If you arent blowing fuses then I doubt its a chafed wire issue, it sounds like you are losing a ground.

Rich
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Friday, December 13th, 2019 AT 10:23 AM
Tiny
HMAC300
  • MECHANIC
  • 113 POSTS
One other ting I forgot is that Chevrolets have a braided ground wire that goes from back of head on pass side to body. Often time when engine work is done that wire is disconnected or not put back on to body. It does screwy things like melting trans cables when a/c heater is on and vehicle gets stuck in drive, Camaros did this quite a bit. But check that as well. If no cable there no ground completion.
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Friday, December 13th, 2019 AT 10:40 AM
Tiny
TOUGHDIVER
  • MECHANIC
  • 224 POSTS
Hi,

From your video you supplied us it looks like you are loosing complete system voltage when you turned your steering wheel. I would double check all battery cables, positive side and negative side on both ends. On the engine, frame, body and starter, and Battery. Check and make sure you have a good clean and tight connections.I am including a wiring diagram below and marked the connections to pay special attention too. Also check around the bell housing with a good flash light. I hope this helps you out and please let us what fixed it.

Thank you
Joe Terwilliger
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Friday, December 13th, 2019 AT 2:01 PM
Tiny
COLLIN LACOBELLI
  • MEMBER
  • 11 POSTS
I ended up finding the problem today after finally getting a warm day to look at the truck. I found the frame to firewall ground strap had broken and the block to frame ground strap could not even be found. So I put on new ones and the problem was gone.
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Thursday, January 2nd, 2020 AT 4:07 PM
Tiny
TOUGHDIVER
  • MECHANIC
  • 224 POSTS
We are happy to help, Thank you for choosing 2CarPros.
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Thursday, January 2nd, 2020 AT 5:42 PM
Tiny
94 TRANSAM
  • MECHANIC
  • 680 POSTS
I would really like to know how putting the steering column in a certain place boils down to those 2 grounds missing. Maybe the wheels turning on the ground torqued some thing? The frame maybe? Weird!
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Thursday, January 2nd, 2020 AT 6:59 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,942 POSTS
Makes sense. Nice work, we are here to help, please use 2CarPros anytime.
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Thursday, January 2nd, 2020 AT 7:53 PM

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