ABS unit

Tiny
YAHWEH
  • MEMBER
  • 2001 CHEVROLET SILVERADO
  • V8
  • 2WD
  • AUTOMATIC
  • 67,000 MILES
This unit continuely runs even when the ignition is off. What precedures or matenance must I take before I take my truck in for service. And is there option to take of this problem. What tools would I need to use that would really help.
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Tuesday, July 29th, 2008 AT 9:36 PM

14 Replies

Tiny
DENNYP
  • EXPERT
The ABS control module needs to be replaced. To get it to shut off, look for the large ABS fuse in the underhood fuse panel. Remove the fuse. You can remove the module from the hydraulic unit without removing any brake lines. You will need a torx bit (I think it's a T-15 or T-20). Remove the torx screws from the top of the module and lift the module off of the hydraulic unit. Put on the new module, bolt it down, and re-install the fuse.
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Wednesday, July 30th, 2008 AT 1:53 PM
Tiny
DENNYP
  • EXPERT
XTooltipElement
Service Information
2001 Chevrolet Chevy K Silverado - 4WD | Sierra, Silverado, Suburban, Tahoe, Yukon (VIN C/K) Service Manual | Brakes | Antilock Brake System | Repair Instructions | Document ID: 720110

Electronic Brake Control Module Replacement
Removal Procedure
Important: After installation, calibrate the new EBCM to the tire size that is appropriate to the vehicle.

Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

Disconnect the negative battery cable.
Raise and suitably support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.

Important: The area around the EHCU MUST be free from loose dirt to prevent contamination of disassembled ABS components.

Thoroughly wash all contaminants from around the EHCU (1).
Disconnect the electrical connectors from the EBCM.
Loosen or remove the bolts (4) securing the EHCU mounting bracket (3) to the frame rail (5).

Gently move the EHCU down enough to remove the mounting screws that fasten the EBCM (2) to the BPMV (1).
Remove the EBCM (2) from the BPMV (1). Removal may require a light amount of force.
Important: Do not use a tool to pry the EBCM or the BPMV. Excessive force will damage the EBCM.

Clean the BPMV to EBCM mounting surfaces with a clean cloth.
Installation Procedure
Important:

" Do not reuse the old mounting screws. Always install new mounting screws with the new EBCM.

" Do not use RTV or any other type of sealant on the EBCM gasket or mating surfaces.

Install the EBCM (2) on to the BPMV (1).
Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

Install the new screws in the EBCM (2).
Tighten
Tighten the screws to 5 N m (39 lb in) in an X-pattern.

Install or tighten the EHCU bracket mounting bolts (4).
Tighten
Tighten the EHCU bracket mounting bolts to 25 N m (18 lb ft).

Connect the electrical connectors to the EBCM.
Lower the vehicle.
Connect the negative battery cable.
Revise the tire calibration using the Scan Tool Tire Size Calibration function.
Return to Diagnostic Starting Point - Antilock Brake System .
© 2008 General Motors Corporation. All rights reserved.


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Wednesday, July 30th, 2008 AT 1:58 PM
Tiny
FRIARTUT
  • MEMBER
  • 2001 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 70,000 MILES
Occasionally when I apply the brakes, if feels like the anti-lock is kicking in. This is happening on dry pavement.
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Thursday, May 16th, 2019 AT 1:03 PM (Merged)
Tiny
MERLIN2021
  • EXPERT
If the ABS light is off, are you turning the wheel as this happens? If yes, check hub/wheel bearings for play.
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Thursday, May 16th, 2019 AT 1:04 PM (Merged)
Tiny
QUAGMIRE86
  • MEMBER
I had the same issue with my 2000 3/4 ton. The problem was that the ABS sensor, which is located at each front wheel bearing assembly (only one side caused the problem) was going "Out of range" due to corrosion. It was a simple fix (ie no money). What happened/happens is that the ABS sensor (which is a magnet in a plastic housing), the item is bolted to the wheel bearing housing, and if you live in an area that uses salt on the roads will cause corrosion. Rust will begin to form on the top of the wheel bearing (between the housing and the sensor). That little bit of rust will push the sensor up and the magnet will not read the toothed ring gear inside the wheel bearing housing. There is one bolt (8mm I think) that retains the sensor, take it off and carefully twist and pull the sensor straight up out of the housing. When it is out, put a cotton ball in the hole and use a knife or other instrument to scrape the rust off the housing (the cotton ball is to keep the rust from falling in the open hole of the wheel bearing). Once you get the big chunks of rust off, use a wire brush to clean the area real well. Put a film of grease on the outside of the sensor (that goes into the hole), take the cotton ball out and re-insert the sensor back into the hole. Affix the retaing bolt and (after you put the wheel back on) take it for a test ride. You will say."Holy monkey-butt, that was easy and cheap". It worked for me.
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Thursday, May 16th, 2019 AT 1:04 PM (Merged)
Tiny
FRIARTUT
  • MEMBER
The light is off, and it happens when the wheels are straight.
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Thursday, May 16th, 2019 AT 1:04 PM (Merged)
Tiny
FRIARTUT
  • MEMBER
Thanks. I'll give that a try.
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Thursday, May 16th, 2019 AT 1:04 PM (Merged)
Tiny
QUAGMIRE86
  • MEMBER
Let us know how you made out with the repair.
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Thursday, May 16th, 2019 AT 1:04 PM (Merged)
Tiny
FRIARTUT
  • MEMBER
Well it did work, but now the abs light is on. Any suggestions? It was a little harder than I expected, the dirt road I live on is hell on brakes. I had to heat the calipers to break the bolts loose.
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Thursday, May 16th, 2019 AT 1:04 PM (Merged)
Tiny
GENE P
  • MEMBER
  • 2004 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 63,000 MILES
1st time here, hello my abs has begun acting up & it does not always happen but on dry roads just before I stop the ABS will kick in any T.S.B's out or your thoughts? Thank you Gene.
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Thursday, May 16th, 2019 AT 1:04 PM (Merged)
Tiny
BRIAN 1
  • MEMBER
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.
This was a common problem on these vehicles.
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Thursday, May 16th, 2019 AT 1:04 PM (Merged)
Tiny
MERLIN2021
  • EXPERT
Well. Using a torch on calipers is not a good idea. Seal may be leaking, is the red brake light on?
And if you followed the other guys advice, you may have damaged the sensor, grab an OHM meter, unplug the sensor from the harness and take a reading, I think yours should be about 2300 ohms, but I'll see if I can find the spec.
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Thursday, May 16th, 2019 AT 1:04 PM (Merged)
Tiny
QUAGMIRE86
  • MEMBER
Can you put it on a code reader and find out what code it is showing? It may be a short or open code on the sensor (may be the plastic housing got cracked during procedure). I feel silly asking, but you did re-connect the ABS sensor back into the wiring harness right? (Assuming you disconnected it at any time during your previous maintenance). I'm at work right now and can't give you the restistance reading on my sensor.

Oh, and I agree with merlin2021. Heating a caliper is scetchy at best. In my younger days, I did that and ended up exploding the re-inforced rubber line that attaches to the caliper. Yeah. My head was in the wheel well when it happened. Very, very loud (ouch). :
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Thursday, May 16th, 2019 AT 1:04 PM (Merged)
Tiny
MERLIN2021
  • EXPERT
Here's the scoop on whell speed sensors:
DTC C0221, DTC C0222, DTC C0223, DTC C0224, DTC C0225, DTC C0226, DTC C0227: WHEEL SPEED SENSOR CIRCUIT MALFUNCTION 1. Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK under DIAGNOSIS & TESTING. After performing diagnostic system check, go to next step. 2. Install scan tool. Turn ignition on. Drive vehicle at speeds greater than 20 MPH. Recheck DTCs. If DTC resets, go to next step. If DTC does not reset, problem is intermittent. 3. Raise and support vehicle. Disconnect wheel speed sensor harness connector. Using a DVOM, check resistance of wheel speed sensor. If resistance is 700-2000 ohms, go to next step. If resistance is not 700-2000 ohms, go to step 8. 4. Manually spin wheel as fast as possible. Using a DVOM, measure AC voltage generated by sensor as wheel spins. If voltage reading is greater than 100 mV, go to next step. If voltage reading is not greater than 100 mV, go to step 8. 5. Check for poor connections at wheel speed sensor harness connector. Repair as necessary. After repairs, go to step 10. If connections are okay, go to next step. 6. Disconnect wheel speed sensor harness connector. Check circuit for open, short to ground, short to voltage or shorted together. Repair as necessary. After repairs, go to step 10. If circuit is okay, go to next step. 7. Check for poor connections at EBCM harness connector. Repair as necessary. After repairs, go to step 10. If connections are okay, go to step 9. 8. Replace wheel speed sensor. After replacing sensor, go to step 10. 9. Replace EBCM. After replacing EBCM, go to next step. 10. Using scan tool, clear DTCs. Operate vehicle at speeds greater than 20 MPH. Recheck DTCs. If DTC resets, go to step 3. If DTC does not reset, system is okay.
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Thursday, May 16th, 2019 AT 1:04 PM (Merged)

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