2002 Sierra 4x4 Abs Problem

jlamson · September 6, 2009

I have a 2002 GMC Sierra 4x4 Ext Cab Z-71 w/4.8 engine. I've had this problem where the ABS comes on every time I hit the brakes, whether dry pavement or on a slippery surface. I took it to the GM dealer, and when they ran my VIN, it came back that the recall was done on it back in 2005. So I figure they did a lousy job, as the problems began in 2007.

So far I have pulled the ABS fuse so I can at least stop my truck without the worry of plowing into the car in front of me.

What do I need to do to fix it? Is it the ABS sensor that is bad? I am pretty sure my troubles are with the front left wheel.

Thanks,

--Jim

glasses97 · October 2, 2009

Just got done repairing that problem. There is a TSB not a recall. Broke both sensors taking them out as they were rusted into the bore. I used a 3/8 lag bolt to pull the broken sleave out of the the bore. Be very careful to not get any dirt into the hole or you will be replacing a hub in the near future. Check the voltage coming off of the sensor as the bulletin say to do. The sensors are not expensive, I paid $55 canadian a piece. The TSB is below. Good Luck

Bulletin No.: 03-05-25-007C

Date: May 16, 2006

TECHNICAL

Subject:

Antilock Brake (ABS) Activation At Low Speeds (Clean Wheel Speed Sensor Mounting Surface)

Models:

2002-2006 Cadillac Escalade, Escalade EXT

2003-2006 Cadillac Escalade ESV

1999-2006 Chevrolet Silverado

2001-2006 Chevrolet Suburban, Tahoe

2002-2006 Chevrolet Avalanche

2003-2006 Chevrolet Express

1999-2006 GMC Sierra

2001-2006 GMC Yukon, Yukon Denali, Yukon XL, Yukon Denali XL

2003-2006 GMC Savana

2003-2006 HUMMER H2

Supercede:

This bulletin is being revised to provide additional warranty information. Please discard Corporate Bulletin Number 03-05-25-007B (Section 05 - Brakes).

Condition

Some customers may comment on ABS activation at low speeds, usually below 8 km/h (5 mph). Upon investigation, the technician will find no DTCs set.

Cause

The cause of this condition may be an increased air gap between the wheel speed sensor and the hub reluctor ring due to rust and debris built up on the sensor mounting surface.

Correction

Measure AC voltage and clean the wheel speed sensor mounting surfaces.

1.Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in the General Information sub-section of the Service Manual.

2.Disconnect both the front wheel speed sensor connectors at the frame and harness.

3.Place a Digital Volt Meter (DVM) across the terminals of each wheel speed sensor connector.

4.Rotate the wheel clockwise approximately one revolution per second. The minimum reading should be at least 350 ACmV's. If the reading is less than 350 ACmV's, remove the wheel speed sensor. Refer to the applicable Wheel Speed Sensor Replacement procedure in the ABS sub-section of the Service Manual.

5.Plug the wheel speed sensor bore in order to prevent debris from falling into the hub during service.

6.Clean the wheel speed sensor mounting surface using a wire brush, sand paper, emery cloth, scotch brite, or other suitable material. Be sure to thoroughly clean the wheel speed sensor surface. There should be no rust or corrosion.

7.Check the sensor head to determine if it has been warped/distorted due to the corrosion build up or other causes. Check the mounting surface on the sensor head for flatness by placing it on the edge of a metal machinists scale or other suitable straight edge to measure the flatness. Check the sensor for flatness in multiple (minimum 3) positions/directions. If the sensor head is distorted, replace the sensor.

8.Apply (spray) two thin coats of the specified rust penetrating lubricant (corrosion inhibitor) to the complete sensor mounting surface on the bearing hub. Allow to dry for 3-5 minutes between coats. Use ONLY Rust Penetrating Lubricant, P/N 89022217 (Canadian P/N 89022218).

9.When the corrosion inhibitor is dry to the touch (about 10 minutes), apply a thin layer of bearing grease to the hub surface and sensor 0-ring prior to sensor installation. Use ONLY Wheel Bearing Lubricant, P/N 01051344 (Canadian P/N 993037).

10.Install either the original sensor or a new one in the hub. Ensure that the sensor is seated flush against the hub. Refer to the applicable Wheel Speed Sensor Replacement procedure in the ABS sub-section of the Service Manual.

11.Place the DVM across the sensor terminals and recheck the voltage while rotating the wheel. The voltage should now read at least 350 ACmV's.

Parts Information

Warranty Information