TRANS fuse blown

Tiny
CRAIGMEMMERT
  • MEMBER
  • 1993 GMC VAN
  • V8
  • 2WD
  • AUTOMATIC
  • 100,406 MILES
I have a 1993 GMC Vandura 2500 with the 5.7 TBI engine. It has 100,406 original miles. Recently, while I was driving "in-town", it lost power and rolled to a stop. It would not restart. I assumed the fuel pump had failed, so I trailered it home. Upon further investigation, I realized the fuel pump was indeed working properly, but the injectors were NOT pulsing. The engine would fire and run on a shot of starting fluid, but the injectors were not delivering fuel. As it turns out, there was no voltage to the injectors via either the white or red wires. I traced the problem back to a blown fuse (labeled TRANS) in the fuse block. I replaced the fuse, and upon turning the ignition switch to the "ON" position, the new fuse blew instantly. Frustrated with the scenario, I disconnected all the electrical connectors on the transmission, replaced the fuse, and turned the key to the "ON" position once more. SUCCESS! This time the fuse DID NOT blow. The engine started and ran just as it is supposed to. With the engine running, I climbed back under the van and reconnected the speedometer wires. Still running, I moved to the passenger side and reconnected the round grey plug. The instant the connection was made, the engine died. Once again, the fuse was blown and the injectors dead. What could possibly have happened, inside the transmission, to cause this problem? What does the voltage, going through the TRANS fuse, actually supply power to inside the transmission? Is this a common problem? Any insight would be very much appreciated.
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Friday, April 22nd, 2011 AT 2:33 AM

3 Replies

Tiny
KHLOW2008
  • EXPERT
That is some great diagnostic works and it has made the problem very clear and easily understood.

Attached are the wiring schematics for the fuse.

Faulty solenoids. Any of the solenoids could be bad and shorted to ground. You can test the solenoids individually with the aid of a DVOM.

Unplug the connector and test the test the range mode and solenoid wires for shorting to ground.

If none is shorted to ground, test the 3 wires going to the PCM for shorting to ground.

Nor sure if this is a common problem.
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Friday, April 22nd, 2011 AT 12:21 PM
Tiny
CRAIGMEMMERT
  • MEMBER
Problem resolved. As it turns out, one of the pink (hot) wires, in the internal transmission wiring harness, had a short-to-ground. It doesn't appear that the transmission pan had ever been removed, prior to my taking it off (which requires removal of the transmission cross member). I believe this problem, to be the fault of the original factory assembler/installer. The wiring harness is supposed to be contained within the black plastic routing enclosure, which leads to all the various solenoids. One of the pink wires was actually on the outside or the enclosure, and pinched between it and the valve body. Ultimately, the insulation on the wire was compromised, and the copper wire made contact with the aluminum valve body, resulting in a dead short. I replaced the wiring harness and the transmission functions perfectly. Thank you for your valuable insight.
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Sunday, May 8th, 2011 AT 3:55 PM
Tiny
KHLOW2008
  • EXPERT
You're welcome and glad the problem has been fixed.

Have a nice day.
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Sunday, May 8th, 2011 AT 8:07 PM

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