ABS is coming on? - Brake pedal judder?

It sounds like one of the sensors has gone out.

Here is a guide to help you test and then replace the sensor if it is found to be bad:

https://www.2carpros.com/articles/abs-wheel-speed-sensor-test

and

https://www.2carpros.com/articles/how-to-replace-an-abs-wheel-speed-sensor

Please let us know what happens and upload pictures or videos of the problem.

Cheers, Ken

This looks like the ABS control module is going out because both of these codes are pointing toward that.

Here is a guide to give you an idea of what you are in for when doing the job

https://www.2carpros.com/articles/how-to-replace-a-abs-controller

Please let us know what you find.

Cheers, Ken

Remove the abs sensors from the hub assemblies. Clean the mounting surface with a wire brush. Reinstall the sensors to the hubs. Test drive the vehicle. If this doesn't work, replace the sensors. They are available at your local dealership.

Check the ABS sensors. Chances are they are dirty, have oil on them and the sensor thinks the stator has stopped. As a result, it turns on the abs.

Let me know what you find.

Joe

You can get ABS codes, but your scanner needs to be able to read them. If you have a basic scanner, it is most likely designed to read engine codes only. Chances are it is a sensor on one of the wheels that is bad.

It is a speed sensor, however, they are ABS sensors. If you have 4 wheel ABS, each wheel will have a sensor. If the light is on, have the computer scanned to identify where the problem is coming from. Most parts stores will do it for free.

I believe you do. Check behind the front backing plates (behind rotors) for wiring. Make sure nothing is damaged to the sensors. Wiring can get damaged. Also, make sure the stater isn't overly dirty.

Is it happening only at slow speeds? If so, check the sensors at each wheel and clean them off. I have found that if they get dirty, they loose contact with the reluctor on the axle at slow speeds and actuate the ABS.

Let me know if this helps.

Joe

The computer thinks a wheel is locking up, typically due to the signal from a wheel speed sensor dropping out. The fastest way to figure out which one is to watch them with a scanner during a test drive.

This is actually a very common problem on these trucks, from 97-05 was most common. Check for a loose wheel bearing, if there tight follow this, Antilock Brake (ABS) Activation At Low Speeds (Clean Wheel Speed Sensor Mounting Surface)

Models:
1999-2000 Cadillac Escalade
1995-1999 Chevrolet Silverado (Old Style)
1995-2000 Chevrolet Suburban, Tahoe (Old Style)
1995-2003 Chevrolet Astro Van, Blazer, S10
1995-1999 GMC Sierra (Old Style)
1995-2000 GMC Yukon, Yukon XL (Old Style)
1995-2001 GMC Envoy, Jimmy
1995-2003 GMC Safari Van, Sonoma
1995-2001 Oldsmobile Bravada

Supercede:

This bulletin is being revised to update the correction and warranty information. Please discard Corporate Bulletin Number 02-05-25-006A (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 wheel speed sensor mounting surfaces.

1. Raise the vehicle on a hoist.

2. Disconnect both the front wheel speed sensor harness connectors.

3. Place a DVM across the terminals of each sensor connector.

4. Rotate the wheel with hand speed and measure the ACmV's. The reading should be at least 350 ACmV's.

5. If the reading is between 200 and 350 ACmV's, remove the wheel, caliper and rotor in order to gain access to the speed sensor.

6. Remove the wheel speed sensor and plug the hole to prevent debris from falling into the hub during service.

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

8. 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.

9. 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).

10. 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).

11. Install either the original sensor or a new one in the hub and secure the sensor. Ensure that the sensor is seated flush against the hub.

12. Install the rotor, the caliper and the wheel.

13. Place the DVM across the sensor terminals and recheck the voltage while rotating the wheel by hand. The voltage should now read at least 350 ACmV's. Post back with what you find.