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Author Topic: ABS Sensor Problem???  (Read 29222 times)
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Afcajax18
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« on: March 08, 2011, 07:02:56 AM »

I am having a problem in my 06' Equinox.  When I am braking down to a very slow speed (almost at a complete stop) it seems like the ABS kicks on for no reason.  The car makes a buzzing noise like something electronic kicks on, just like the ABS system, the pedal pushes back on my foot.  The brakes work fine at any other speed, and the car always stops fine.  This does not occur everytime I stop, I would say 7 out of 10 times.  There is no "check engine" or "ABS" light on on the dash.  Anyone have any thoughts?  Thanks
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msb725
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« Reply #1 on: March 08, 2011, 07:41:16 AM »

Might be speed sensor in one of the wheels. Happened in wifes 2006 Torrent.

Sent from my DROIDX using Tapatalk
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ChevyMgr
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« Reply #2 on: March 08, 2011, 07:42:15 AM »

Rear brakes being mis-adjusted could cause this.
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« Reply #3 on: March 25, 2011, 11:41:24 AM »

I would have to agree with the previous posts that the best place to start is with the breaks. If this does not seem to solve the issue, then I would recommend that you contact your local dealership for more specific information. Please feel free to keep me informed with any further developments. Thank you.

Tricia, GM Customer Service.
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revolutionair
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« Reply #4 on: June 14, 2011, 04:13:56 PM »

I have the same exaact problem with my 06 Equinox.  I am probably going to have it checked at the dealer later this week, and I will update with the answer.  I think I had the same problem with my 01 Grand Am, and it was the speed sensor.  I cleaned it and put it back together with some lithium grease (i think that was what it was) and that did the trick.  Does anyone know if these are in the front and back, or just the front?  And what do they look like?
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« Reply #5 on: June 16, 2011, 10:45:46 AM »

I have the same exaact problem with my 06 Equinox.  I am probably going to have it checked at the dealer later this week, and I will update with the answer.  I think I had the same problem with my 01 Grand Am, and it was the speed sensor.  I cleaned it and put it back together with some lithium grease (i think that was what it was) and that did the trick.  Does anyone know if these are in the front and back, or just the front?  And what do they look like?

I am glad to hear that you are planning to work with your dealer regarding this concern. Please feel free to keep me posted. I can also look into the locate of this for you with the VIN of the vehicle.  You can contact me via private message as well. Thank you in advance.

Tricia, GM Customer Service.
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cseay1
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« Reply #6 on: August 10, 2011, 11:58:42 AM »

I own a 2006 Equinox LS AWD.  I experienced the same concern with the ABS activating during low speed braking, but it took a long time to set a trouble code (the ABS/TC warning lamps did not come on for a long time, and when the finally did they would only come on briefly then go out).  The code set for a LF speed sensor fault.  I replaced the LF wheel hub & sensor assembly with an aftermarket part.  The code cleared out but it continued to cause ABS activation at low speed.  Watching the speed signals with a scan tool while driving, it showed all four sensors reading properly but indicating that the vehicle speed was exactly 2X what the actual speed was (60 mph read as 120 mph).  Still no codes no lights.  Thinking the EBCM may have a fault, installed a new EBCM, but problems persisted.  Finally observed LF speed sensor signal drop out, so thinking had defective hub/sensor replaced with another aftermarket.  This one was even worse.  Finally replaced with genuine gm part (which strangely enough had the exact same markings as the two previouse aftermarket parts) and knock on wood no problems since.  But scan tool still shows that speed sensors showing vehicle speed as 2X actual.  Don't suspect faulty VSS at transfercase because speedo is reading correct.  Anyone else experience this?
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Rit
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« Reply #7 on: August 10, 2011, 01:28:49 PM »

You sound extremely knowledgeable - welcome to the Forum.
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cseay1
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« Reply #8 on: August 11, 2011, 12:56:12 PM »

Thanks for the welcome ..

Alas after several days of driving fine the ABS started acting up again.  No ABS/TC light but did set trouble code again for LF wheel speed sensor.  I should note that prior to all of this the circuit was ohmed from sensor to EBCM and checked ok .. no breaks observed in wiring.  Just replaced the GM bearing (which again looked IDENTICAL to the previous three BCA/National bearings, even felt the same - could feel CLICK-CLICK-CLICK as sensor passed teeth on tone ring) with a Carquest bearing which looked completely different, was obviously of different manufacturer, and felt smooth - no clicks.  Should further note that after removing the three previous defective bearings they all show a blue heat ring around the hub, like they are getting too hot (incorrect tolerances?  no grease in the bearing?) .. Carquest bearing so far doing good .. But still getting 2X indicated speed through scan tool.  If it happens again I give up .. it is either going to the dealer for repairs or trade in.  It's a shame, because up until now this has been a great vehicle - 86,000 miles.
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cseay1
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« Reply #9 on: August 14, 2011, 04:57:52 AM »

Too good to be true .. ABS began activating again at low speed braking, but still no warning light or trouble code .. Will pull ABS fuse and live without ABS/TC and just ignore the warning lights on the dash until can afford to take to Chevrolet dealer for additional diagnosis
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cseay1
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« Reply #10 on: August 18, 2011, 06:51:53 AM »

Finally may have some resolution ..

Took to local Chevrolet Dealer .. they diagnosed the fault as being in the harness between the left front abs speed sensor and the electronic brake control module (which would make sense for the signal dropping out to the left front and continually setting codes for the left front) .. they replaced the harness .. was charged 168.00 labor plus 83.49 parts making a total with tax of $255.66 .. we are going to try it out on a trip next week from home in Virginia to Disney World in Florida (approx 1700 miles round trip) so that will be the test to see if this is the fix or not.
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boxy_eh
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« Reply #11 on: August 27, 2011, 07:17:39 PM »

Hello cseay1,

I was just wondering if the dealer replaced both harnesses from the left front sensor to the computer, or just one of them.  I have a 2006 Equinox that has the exact same problems that you have, well, until I pulled the fuse!

Thanks.
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rortega11
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« Reply #12 on: August 12, 2012, 10:13:57 AM »

which fuse did you pull ? i found 3 that are related to the
 ABS system
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deadbug
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« Reply #13 on: March 15, 2015, 02:07:27 AM »

I had a similar experience with a 2002 Denali around 130K.  Upon pulling into parking spot, front brakes (possibly rh only) would grind and thump in the pedal.  Sometime the ABS light would come on, sometimes not, but it never stayed on.  Eventually for fear of damaging the rotor, I took it to GM dealership.  Diagnosis: front wheel sensor corrosion.  Result replaced both as lh side was in similar state.  No problems afterwards, and not unreasonable expense considering the miles and salty winters.

NOTE:  Service people can mean one to two things when they say speed sensor.  The sensor is exactly than, it reads the rpm of the individual wheel providing data for both ABS and TC.
          The second item they may be referring to is the ring in the back of the hub that the sensor actually reads rotational data from.  These over time often get covered in salt, grease, and other
           road debris preventing the sensor from getting a proper reading.  Ask your technician which it is.  One is a simple (not cheap) wire harness change.  The other generally involves purchasing new
          hubs which is considerably more costly.

The good news is on most vehicles, a small portion on the ring on the back side of the rotor is slightly accessible and debris and salt can be cleaned off.  You can remove the hub assembly to access it all or you can raise the wheel of the ground, scrub what is accessible with a toothbrush or brass brush, rotate the wheel to do another section and so forth until you have completed 360 degrees.  Bear in mind the other 3 wheels will likely be in the same condition.  Do NOT use a steel brush as the magnetism of the assembly will retain wire pieces will be difficult to remove while the hub is on the vehicle and will interfere with the sensor readings.

Once you have them cleaned, and if indeed solved the issue, some have had success with blasting the exposed portion of the rings each time they handle a car wash spray wand, hopefully maintaining all 360 degrees over time.

With all that being said, if you go to a service shop, especially with a 2010 through 2012 Equinox take this document with you to prevent paying for a bunch of parts and labor that weren't the actual problem:

Vehicle: 2011 Chevrolet Equinox
Nature of Defect:
SERVICE BRAKES, HYDRAULIC:ANTILOCK:WHEEL SPEED SENSOR
Bulletin Number:
PIT-5171
Bulletin Date:
Aug 2012
Summary:
GMC/CHEVROLET: A COMMUNICATION FAULT, REGARDING SERVICE STABILITY TRACTION AND ABS REAR WHEEL SPEED DTC OR CHASSIS EXPANSION BUS, WHICH IS RELATED TO AN INTERNAL WIRE BREAK INSIDE WIRE HARNESS INSULATION TO X411 CONNECTOR. MODELS 2010-2 ( NHTSA ITEM NUMBER - 10045959 )

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KarenEquinox
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« Reply #14 on: April 28, 2015, 10:38:52 AM »

We are having similar problems.  C0035 Code (LF speed sensor) ABS cycling (occaisionnally) when brake pedal depressed.  Get ABS and Traction control lights.  Scanner shows correct wheel speed readings on all four wheels.  Have replaced LF bearing and sensor assembly twice.  Have not replaced the wiring from the sensor to connector under frame below EBTCM, but it ohms out to 1550 ohms, and same as just sensor pigtail.  The problem is that wiring (blue and yellow) go into large wire bundle just below module, so I cannot check the harness further without diagram.  (Maybe I have answered my own question here)... but any help would be appreciated...
When last post says Chevy replaced harness, the question is which harness, although our problem may be different.  Thanks
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KarenEquinox
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« Reply #15 on: May 12, 2015, 02:20:31 PM »

Hello, thought I would follow up on the fix for our 2005 Equinox with ABS and traction control lights illuminated, cycling anti-skid and codes for speed sensors Left Front (C0035 and C0036).  I ran a scanner on the graphs for the speed sensors and found the LF sensor dropping the signal on the graph.  After doing all the wiring tests and replacing the LF bearing assembly, I noted a shim on the LF sensor that increased the gap between the sensor and teeth on the bearing assembly.  This shim was shipped on the assembly and should have set the proper gap for the sensor.  I believe the shim set too wide a gap and the signal dropped out, so I measured the sensor length and distance to the teeth for both front sensors and removed the shim, checking to ensure there was no contact between the sensor and teeth.  Have run the vehicle for 100 miles without a drop out on the graphs nor any lights.  Believe the problem has been solved.
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Chas
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« Reply #16 on: May 12, 2015, 02:49:32 PM »

Hello, thought I would follow up on the fix for our 2005 Equinox with ABS and traction control lights illuminated, cycling anti-skid and codes for speed sensors Left Front (C0035 and C0036).  I ran a scanner on the graphs for the speed sensors and found the LF sensor dropping the signal on the graph.  After doing all the wiring tests and replacing the LF bearing assembly, I noted a shim on the LF sensor that increased the gap between the sensor and teeth on the bearing assembly.  This shim was shipped on the assembly and should have set the proper gap for the sensor.  I believe the shim set too wide a gap and the signal dropped out, so I measured the sensor length and distance to the teeth for both front sensors and removed the shim, checking to ensure there was no contact between the sensor and teeth.  Have run the vehicle for 100 miles without a drop out on the graphs nor any lights.  Believe the problem has been solved.

Great update - two things if I may ask:
1 - could you share any pictures of the shim?
2 - what scanner did you use to see the graphs for the speed sensors?
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KarenEquinox
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« Reply #17 on: May 16, 2015, 06:42:46 PM »

Update on 05 Equinox.  Worked fine for 2 weeks but now C0035 and C0036 again with ABS and Traction control lights and cycling ABS.  To answer your questions, (sorry it took a while to find the shim), attached are two photos. One is the graph off my solus pro scanner. you can see the signal drop in the LF graph, and the other is a photo of the shim.  Car returned today with same problem.  We have had a lot of rain lately, so will re check wiring.  Will probably try saltwater spray on wiring.  BTW I changed the LF sensor to the right Front last time, so I do not believe the sensor is the problem.  Still will look at clearance between sensor and teeth on hub.  Any ideas welcome
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mcg75
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« Reply #18 on: May 17, 2015, 05:58:31 AM »

Update on 05 Equinox.  Worked fine for 2 weeks but now C0035 and C0036 again with ABS and Traction control lights and cycling ABS.  To answer your questions, (sorry it took a while to find the shim), attached are two photos. One is the graph off my solus pro scanner. you can see the signal drop in the LF graph, and the other is a photo of the shim.  Car returned today with same problem.  We have had a lot of rain lately, so will re check wiring.  Will probably try saltwater spray on wiring.  BTW I changed the LF sensor to the right Front last time, so I do not believe the sensor is the problem.  Still will look at clearance between sensor and teeth on hub.  Any ideas welcome

I've never seen a wiring issue cause that ever.  With wiring, you either have the signal or you don't.  Yours is keeping the signal.  If the signal was lost, the abs and trac lights would come on and the system would shut itself off until it rechecks for signal at next startup.

I have seen this happen with cheap aftermarket replacement bearings.  The height of the teeth or the gap between may be off just enough to cause issue.   

I think you're on the right track looking at the gap between the sensor and the teeth.  We've fixed this exact issue many times by removing the sensor and cleaning corrosion underneath it that was pushing it up widening the gap.  Obviously corrosion has nothing to do with yours because it's recently new.   

   
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KarenEquinox
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« Reply #19 on: May 21, 2015, 12:33:20 PM »

Update for 2005 Equinox with ABS, Traction light and C0035 code. 
Ok, so since I figured it was in the gap for the sensor to ring (and got similar feedback from forum) so I decided to replace the bearing assembly (again, this will be the second I have replaced on this car).  That would fix any gap issues.  Bought one from Autozone and replaced it.  Fine for about 100 miles, then ABS light again.  Also rainy when driver reported ABS light, so will  go back to wiring.  Believe I will make a wire myself and run it from the sensor plug to the ABS control unit (Pins 6 and 7).

Appreciate the feed back from forum... any ideas
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