Where is it located ABS Module 2000 Expidition

Electronic Brake Control Module (EBCM)
Left rear of the engine compartment, near the left strut tower

in the engine bay on the right hand side attached to the abs pump

images for 2002 Tahoe abs relay location

Chevy ABS and Brake Dash Light fix - YouTube

? 24:15
https://www.youtube.com/watch?v=Jo76ylqgUR8
Dec 22, 2012 - Uploaded by Skizzot7
This is how to fix intermittent ABS and Brake dash lights on all Chevrolet ... That board is rather robust and is installed external to the vehicle in a location that sits .... I took the module out of a2002 Sierra and it is engineered with no T10 .... ABS Sensor and Harness 2000-06 Chevy Suburban Tahoe GMC ...

How I fixed a Chevy with an Abs and Brake light on - YouTube

images for 2002 tahoe wiring

It uses the ABS wheel speed sensors through the ABS control module I do believe.

Sounds like a Faulty ABS module but it could be a caliper if any of your pads or shoes are worn too low. Have the ABS module tested. It is located under the Master Cylinder in most cases and has all the lines that run to your calipers coming out of it.

it will cost about a $100 to get it diagnosed. They will then tell you how much more it will cost to fix it. You can still drive the car with the light on. You just don't have antiskid capabilities.

Your ABS control module has failed. It can fail in two areas.. either the fuse controlling it which is a large fuse and located in the engine cmpartment on most vehicles or the actual ABS actuator control module which is a computer driven box located on bottom of vehicle that pumps the brakes to make them antilock (think how in the 70s you were told to pump brakes, now the car pumps its own brakes) The computer module is what burns out leaving you without ABS but not brakes themselves. Your car indicates this by showing you an ABS error light and a brake light. You are not in danger by driving the vehicle you just will NOT have antilock brakes in the event of an accident and could slide if you lock the brakes by slamming them down. Check your owners manual for the fuse location in your vehicle and inspect it. If its burned out replace it and see if this fixes the problem This is a 3-7 dollar fuse. If that doesnt do the trick unfortunately the repair is very expensive 700+ dollars for a new control unit.

DTC C0121 will set if the valve relay voltage is low or if the relay supply line is at 12 volts when the ABS control module is not requesting it. This DTC will also set if the ABS control module detects three or more solenoid
valve circuits are open or shorted during the self-test.
Cause(s)
A connector terminal is corroded.
The wiring harness is damaged.
The ground terminal is not conducting properly.
The EBCM is defective.
the relay is internal to ABS unit.

The abs control module is located under the hood, on the drivers side, below the master cylinder on the fenderwell. Replacing it can be a hassle, as first you have to break free all the steel brake lines going to it, and it's a bit of a pain to bleed. It has to be done a certain way, or it won't operate normally.

Unfortunately the ABS relay is built into the EBCM. Electronic Brake Control Module. That is located on the frame rail, left side of vehicle and sits on top of the pump. Both parts are likely to be replaced together as getting the module off the pump can be difficult. I recommend a repair facility do this job but it can be done at home. You will likely need to take loose metal brake lines and that can be quite a task also.
Are you getting a code for the relay / EBCM?

Good luck
Please rate my answers if they helped.
Brett