Code U0100 and P0700

diyer2 · August 31, 2016

Was up in the mountains fishing, towing the boat. Got ready to head home, started my truck and the DIC says stability control off, traction control off. Check engine light is on. I'm over a hundred miles from home, hills, winding, twisty roads, mountain passes to travel.

It runs fine, stop at the auto store by the house and they pull code U0100 and P0700. After reading the codes start the truck to go home and the check engine light is gone as well as the icons on the display for traction control and stability control.

Any thoughts?

Will update post when I start the truck again, later today to run some errands probably.

arctictwist · August 31, 2016

I was throwing that code in my 2008 and it ended up being one of the speed sensor cables worn through. Every time it hit the wheel on the bare spot it lit up my dash with warnings and that code was one of the ones that went off.

sonerick · November 13, 2017

OP, did you ever figure out what was causing your issue?

I had a similar experience this weekend: I was in CT, 2 states away from home, in the middle of the woods, and the truck threw the U0100 and P0700 codes and went into limp mode for a bit. I cleared them with a Scangauge and it's been fine since, aside from the POS clunky shifting that I normally experience. The dealership this morning told me there is nothing they can do because I cleared the codes.

carnau · November 14, 2017

On 11/13/2017 at 9:44 AM, sonerick said:

OP, did you ever figure out what was causing your issue?

I had a similar experience this weekend: I was in CT, 2 states away from home, in the middle of the woods, and the truck threw the U0100 and P0700 codes and went into limp mode for a bit. I cleared them with a Scangauge and it's been fine since, aside from the POS clunky shifting that I normally experience. The dealership this morning told me there is nothing they can do because I cleared the codes.

What year is your vehicle?

sonerick · November 14, 2017

2017. I realize this is not the K2XX subforum, but I am trying to gather any and all semi-related info that I can.

carnau · November 15, 2017

The P0700 code is really a generic code saying the Transmission is requesting the light. P0700 - Transmission Control Module Requested MIL Illumination

The U0100 is a Communication code with the Engine Control Module.

U0100 - Lost Communication With Engine Control Module

On a 2017 the way you would want to test this is to go between terminal 6 and terminal 14 of the DLC. You should have 60ohms of resistance because you have a 120 ohm resistor in the ECM and a 120ohm resistor in the High speed bus at the other end of the circuit. If you Don't have 60ohms this is where your problem lies. Either in a module or the wiring.

If this happens and you check the resistance and it isn't 60ohms (and you need to check that with the ignition off when the car hasn't been run for a while or even better if you disconnect the negative cable to the battery) Come back on here and quote this and I will walk you through the steps to find out exactly where your problem is. Hope this helps. I am going to leave a Schematic below.