1988 Suburban v10 5.7L Silverado troubleshooting help

[Moody Blue]

Hello Hello,

And here we go:

My 1988 Suburban just stopped working randomly. No power anywhere except the Headlights/Dome Lights.

I ended up having the vehicle towed to my home, as I was in the parking lot of a hardware store when this happened. I was able to force the linkage to go between park and revers in able to do this, otherwise the truck is completely immobile.

I have spent considerable time chasing wires this was and that way. to put it simply:

the power lead that comes from the junction in the engine compartment, then goes through the firewall and splits off three ways (two to the ignition, one to the fuse block) has power as to be expected at all points. However, in the ignition switch, when switched to "ON/RUN" sends all the power to ground somewhere, meaning nothing gets power. I chased this all around to two locations.

ONE- being the Pink lead form the ignition that splits off three ways (two to the fuse box, one through the firewall to all components that require power while the vehicle is in operation (sensors, etc etc). When I close the circuit from the main power lead to this Pink lead all power dissapears. Leading me to assume there is a short somewhere. There is continuity through this wire everywhere I could find that it goes. Which leads me to believe there is no short. But maybe I am wrong here.

TWO- Being a Tan/White lead that from what I can gather goes form the ignition switch to the ECM. There is continuity from the ignition switch to the connection at the ECM. Hoever when I engage power form the Red incoming lead to the Tan/white lead going to the ECM all power shorts to ground. This happens wether the tan/white lead is connected to the ECM, or not.

In more randomness, sometimes, when I jump power from the red, incoming wire to the pink wire the whole dash will light up, door buzzer works etc. though this is random. I thought I had it all figured out at one point and put the while thing back together. When I put the key in the ignition the buzzer buzzed, the SES light came on and everything else you would expect. When I turn the key to IGN, everything shuts down and it takes a day to get power back anywhere.

Before I rip the whole dash apart, does any of this sound telling in that it could be something simple?

Battery checks out, every ground I can find checks out... I cannot find any frayed wires or evidence that critters moved in and have been tearing it apart.

I do have videos of the issue, I am working on how to share those.

Any Advice would be appreciated!!!!

 

[Broken85]

You have a ground problem I think. Check the ground strap on the back of the engine head that attaches to the firewall under the hood, then check that the motor is ground with a braided strap to the frame. Since you have multiple systems effected at the same time, I would also look at the negative bus board under the dash. There are 4 or 5 leads that ground to it. It is riveted to the driver side pilar wall under the dash over top of the Emergency brake pedal. I usually get to it by taking the dash pad off. sometimes they get corroded and lose contact. It’s a fix.

 

[Ricko1966]

Have you checked and the battery cables? Ots common with dirty battery cables to have just enough continuity to turn on lights but not be able to handle the amperage of the starter. Everything goes away under load,wait awhile and just enough for lights comes back. Put your meter in volts scale on the negative battery POST not the end of the battery cable. Put the other end of your meter on a good ground on the engine,have someone try to crank if the meter reads more than 1volt you have a ground problem. Do the same thing using the positive battery post and the charging lead at the alternator,do you get more than 1 volt? It's a power problem . Technically you should do that at the positive starter post,but 99 percent of the time checking it at the alternator will do.