94 GMC 2500 4X4

jlcronk · August 16, 2006

I am having the following problem with my 1994 GMC 2500 4X4 350 V8 with automatic transmission:

The brake (ABS) light flickers intermittingly and produces these problems. The Cruise control will stop working (the cruise will work fine if ABS light stays off), the windshield wipers will start and stop as the brake light flashes on and off and the engine will misfire (mainly during idle) but does not die.

I have done the following testing:

Replaced the ABS control module that is attached to the master cylinder. Note: the salvage yard had 4 of these on the shelf and none of them solved the problem. I have unplugged the following items from the steering column: cruise control on/off switch, wiper switch, brake light switch, emergency brake light switch and the cruise control module on the firewall. Light still flashes engine still misses. I have also unplugged the bottom (smaller of the two) connectors on the ABS control module light still flashes. When I unplug the large connector light quits flashing and the engine runs fine. The cruise will not work with the ABS box unplugged. I did disconnect the battery several times for approximately two minutes during the above testing to clear any computer codes.

I feel that there must be some kind of short associated with the wires of the large ABS connector. I have checked visually for cracked wires and made sure the wire connections into the back of the plug were tight. I have tried all I can think of but I may not be going in the right direction. Any help with wiring diagrams or other ABS components will be greatly appreciated.

mmmikkke · August 16, 2006

I think you have an intermittent (possibly corroded) ground somewhere. Look for ground points under your dash and also between cab and frame.

jlcronk · August 18, 2006

I think you have an intermittent (possibly corroded) ground somewhere. Look for ground points under your dash and also between cab and frame.

<{POST_SNAPBACK}>

Thanks for the tip on ground wires. I found the main engine harness ground wire had been unhooked from the bell housing for some reason. I attached the ground wire back to the bell housing and all of my electrial problems went away.