1995 K1500 Ext. Cab with 5.7 tbi
I’ve had no issues since owning the truck for 6 years. Otw to work a couple weeks ago I had to slam on the brakes on the highway to avoid hitting the car that pulled in front of me at 65/70 mph. Since that day my truck randomly cuts off when going under 30mph, the cruise control won’t stay locked in place and high and low idling problems and going into OD very quickly.

 

Did you have to swerve to the shoulder or contact anything that would’ve jarred the suspension?

Swerving suddenly could’ve damaged one of the ignition wires that runs up the column and it may be intermittently grounding out or contacting another bare wire.

 

I didn’t come in contact with anything at all. It was just hitting the brakes as hard as I possibly could.

 

That’s certainly a head scratcher. As for wiring, all those components are tied together at the ground at the thermostat housing, but if nothing resulted in the suspension or power train getting jarred, it’s hard to say.

The cruise may be affected by the brake switch not fully returning - you can try pulling back on the pedal to see if that returns.

You can try pulling diagnostic codes - even if the SES isn’t on there could be codes stored that may lead to a diagnosis.

At the OBD plug, Jumper pin B to pin A or to a good ground, then turn the key on engine off and count the blinks of the SES. Note that code 12 (system pass) will be the first code to be displayed, and each code will repeat 3 times before the next one reads out.

Codes are read by looking for a pause between digits, as shown below (a blink is represented by I)

I (pause) II (long pause) I (pause) II (long pause) I (pause) II (long pause)

This readout translates to code 12 being repeated 3 times, then any following codes will be displayed in the same format.

 

I just wanted to add that I actually just looked at a similar problem with a customer truck yesterday. This truck is a 1993 K2500 7.4 but it’s wiring and drive train would be very similar to yours. The issue they were experiencing is the transmission fuse would blow any time they put moderate pressure on the brakes, and it would only happen in motion.

What I found is that the wiring harness for the transmission had come loose and was chafing against the shift linkage for the transfer case. When the brakes were applied hard enough, the harness would slide forward just enough to contact a bare spot on the ignition wire for the transmission and blow the fuse.

The customer never mentioned any driveability concerns other than the transmission defaulting to limp mode when the fuse would blow, but it may be worth it for you to inspect the harness on the transmission and frame rail for areas that have chafed as well.

 

Unlike most folks that just start throwing parts at the truck, I made a checklist and started checking things with multimeter etc..
I seen that the ground strap from frame to cab was brittle and green. I bought a $7 Dorman strap from the help section at Advance Auto and replaced it. Everything went back to normal after that.

 

My anti-lock brake controller (1995 Chevy 4x4 K1500) started affecting cruise control. I disconnected power to brake controller and cruise issues went away.