I had a code 700 when I diagnose my 94 GMC Sierra. That is a transmission control unit problem. What's the best and cheapest way to fix it. can I do it myself?

Russell Varize

Asked by Feb 19, 2014 at 01:47 PM about the 1994 GMC Sierra 1500

Question type: Maintenance & Repair

I was going 65 70 on the freeway
When I noticed I smelt burning wires.
the truck then kind of held back
power while my foot was still on the
gas . it does this every now and then
feels like its locking up on me. tell me
what's going on and what can I do?

2 Answers


Well find the burnt wires first. The '94's have a ECM to run the TBI engine and a separate TCU to control the 4L60e. The TCU is located on the drivers side inner fender. Inspect the wiring. Follow the large harness back to the tranny plug. It may be a good idea to drain your tranny fluid to see what conditon the fluid is in. Also inspect the shift solenoids and wiring on the valve body.


If the wiring looks good you could try replacing the TCU. They are very cheap at the wreckers. Just make sure it's pulled from a 1/2 ton gas with a 4L60e ('93-94). Larger trucks and the 454ss used the 4L80e and the controller is different.

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