testing ABS wheel sensor

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  #1  
Old 12-30-11, 06:19 AM
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testing ABS wheel sensor

2006 Buick Terraza

ABS lite comes on after about 20 feet of driving. Sometimes after warmed up it comes on as soon as its started and stays on even it shut down and restarted. Sometimes can be shut down and restarted and the lite will go off until driven for 20 feet then lite comes on again. If lite is off when idleing the lite will remain off and only come on when put in gear and driven.
Seems to be getting worse.

ABS or AWD will not work when the lite is on

"C0042 Right front wheel speed sensor circuit low"
The wheel sensor is built into the axle hub and it costs $250
I can not get any movement of the wheel bearing and no noise.

I want to test the 2 front sensors and compare.
I will disconnect the front wheel sensors and leave the ignition off.
I have an oscillioscope but im not good with it.
I will hook the scope to the 2 wire connecter coming out of the wheel sensor and turn the wheel hub by hand. It will be in neutral. I will try to turn both front right and left the same speed and compare the scope results. Good sensors should be the same but if the right sensor is not good then should read different.
I think
Any advise on my plan or ideas on how to do the test better or things to check other then what im doing?

thanks.
 
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  #2  
Old 12-30-11, 07:22 AM
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Could very well be the hub sensor failing but sometimes the sensor connection can also become dirty/oxidized, and the wire itself can sometimes get worn from suspension interference issues and broken clips. I would confirm the wire and connector as a first step.
 
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Old 12-30-11, 07:29 AM
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start with pulling sensors out (easy) and cleaning heads. unless you have them like Buick likes them - integral part of hub bearing. then it's tough.
 
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Old 12-30-11, 07:33 AM
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  #5  
Old 12-30-11, 10:20 AM
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Thanks
First thing I did was check the wiring. With the naked eye, and some reading
The wheel sensor is built into the axle hub and it costs $250
06 Buick Terraza
 
  #6  
Old 12-30-11, 10:26 AM
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Your pic got me to thinking.
Next step should be pull the hub right off and take it to the work bench and inspect it and clean it right.
 
  #7  
Old 12-30-11, 05:28 PM
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yeah, for $250, you may want to consider pulling hub bearing out and getting to that sensor head.
 
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Old 12-30-11, 05:35 PM
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keep in mind, crud build up not just on sensor but, also, on ring gears.
 
  #9  
Old 01-03-12, 12:42 PM
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Not sure how far you've gotten but i would test it with the ocilo first. That is the best test you can do. First check them with an ohm meter. If one is 0 or infinity then it's bad. Especially if you can get a ohm reading, usually anywhere between 25-500ohms from the other one. The scope is the next best test. You should see wavey lines that get closer as you spin the wheel faster. If the rf one is much different from the left it's bad.

skeeter
 
  #10  
Old 01-15-12, 03:35 PM
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Update. Pulled hub off and looked very close. One of the wire pins seemed to be a bit green. Cleaned well with a small file and did the female part with a small paper clip. I noticed that one of the two slots where the pins go was looser then the other. This one was the greenish one. I could not fix it to have more tension.I put it together and it worked for about 20 minites untill we went thru a large ice puddle and got it stuck. ABS dont work again. i think we moved the wire again and it lost contact. Good news is I found the problem.
now I will order the harness. The pics show the part has the connector on one end and just wires on the other end.
I do not know where these wires go. I never change one before.
Any leads as to how to change this wire
Thanks
 
  #11  
Old 01-15-12, 07:44 PM
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I am quite sure there is a TSB on this problem. A Google search should bring it to light. Chevroletforum has an Uplander forum (same as Terraza) that I belong to, have a look there as well.
 
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