Outline · [ Standard ] · Linear+ intermittant ABS

[kev2]

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intermittant ABS??
« on: Today at 04:49:18 PM » Quote Modify Remove

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My truck @60k miles
2006 chevy K1500 4.8L auto
frt disk Rr drum...
No codes, no ABS light, brake linings very good,

reciently started and intermittant- at low speed* ABS will engage?

How to trouble shoot? specific Pls
Ideas?

* very low @5mph- hard stop performs GREAT


PS: Why does my stufff NEVER fail at home- only on the road ?? in West Point NY area.

[TECH II]

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#03-05-25-007D: Antilock Brake (ABS) Activation at Low Speeds (Clean Wheel Speed Sensor Mounting Surface) - (May 1, 2009)


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

2007 Chevrolet Silverado Classic

1999-2006 GMC Sierra

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

2003-2006 GMC Savana

2007 GMC Sierra Classic

2003-2006 HUMMER H2




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This bulletin is being revised to add the 2007 Silverado/Sierra Classic models. Please discard Corporate Bulletin Number 03-05-25-007C (Section 05 -- Brakes).


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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.

Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in the General Information sub-section of the Service Manual.
Disconnect both the front wheel speed sensor connectors at the frame and harness.
Place a Digital Volt Meter (DVM) across the terminals of each wheel speed sensor connector.
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.
Plug the wheel speed sensor bore in order to prevent debris from falling into the hub during service.
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.
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.
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 (in Canada, P/N 89022218).
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 O-ring prior to sensor installation. Use ONLY Wheel Bearing Lubricant, P/N 01051344 (in Canada, P/N 993037).
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.
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.

[kev2]

TECH II Looks the sensors are secured with a bolt thru head of sensor- how does the air gap get adjusted and to what dimension? ??

any tips on locating which wheel? -as its intermittant and NO code?

[TECH II]

didn't you read the TSB I printed?

[kev2]

yes?

[gmctech2000]

The sensor is bolted to the outside flange on the hub, the air gap gets changed when corrosion builds up under the sensor mounting point and lifts it up, which creates the difference in air gap that the EBCM sees and activates the ABS....if recall hasnt been done yet, might be worth a trip the dealer to get it cheked out...its a very scary feeling when it happens...

[kev2]

finally got ABS light while turning tight left....
light =code which ID'd LF narrowing it down ...
clean and did not pass minimum reading as per TechII info

R&R'd all good now-

well there is the intermediate steering shaft noise-


GMTECH- this is a TSB ....I did not get a recall?

[gmctech2000]

There was a recall but not every truck got it, only did certain years...email my your vin, i will run it through to see if it applies...but i am pretty sure recall didnt apply to 2005 or newer trucks...atleast not yet....

This post has been edited by gmctech2000: Nov 4 2009, 12:16 PM

[kev2]

INFO SENT........ THANKS

[gmctech2000]

No prob Kev, I tried sending the info i got, hopefully it came through...

[kev2]

tks got it