# Tcs



## lemley98 (Mar 19, 2012)

I have a 2008 Impala, The TCS activates for no reason.can someone tell me why?It happens when you pull out ( no icey or wet conditions) If its the sensor ,How can you tell which one to replace? thanks


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## cjm94 (Sep 25, 2011)

Sounds like an erratic speed sensor. You will need to watch each sensor with a scan tool to see which one drops out. Unless it failed long enough to set a code. It usually will not if it only drops at low speed the computer just thinks the wheel is slipping.


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## lemley98 (Mar 19, 2012)

Are the sensors only on the front wheels? Would it be wise to buy one and try on each wheel, to see if that cures the problem? thanks


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## cjm94 (Sep 25, 2011)

No they are on all 4. Not sure on 08 impala not all are service separate from the wheal bearing. It will be cheaper to have someone diagnose it than just throwing parts at it.


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## Marqed97 (Mar 19, 2011)

cjm94 said:


> No they are on all 4. Not sure on 08 impala not all are service separate from the wheal bearing. It will be cheaper to have someone diagnose it than just throwing parts at it.


Absolutely correct. Have somebody diagnose it then replace it yourself if you like. 08 Impalas have them built into the bearing hub assemblies. Very common issue.


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## iamrfixit (Jan 30, 2011)

Could also be the wiring harness running to the sensors, these often fail on the front wheels due to the wire repeatedly bending as the front wheels are steered back and forth over the years.

Changing the wheel bearing/hub assembly is not too difficult if you do much auto work. The job often generates significant profit for the shop; many of which seem to do little more than just throw the parts at it for you.


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## SPS-1 (Oct 21, 2008)

Are all your tires the original size? If the tires were designed to be all the same size, and you swap out one or more tires to different sizes, the computer will "see" some wheels running at a different speed than the others, and may interpret this as a wheel spinning.


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## 47_47 (Sep 11, 2007)

Are you getting wheel slip (worn tires)?


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## Lotek (Apr 24, 2013)

Definitely one to diagnose rather than spin the wheel of parts, not too difficult to isolate a wheel with a scan tool and multimeter, but harness vs sensor can be a tossup, and proper splicing is critical with the harness repair.


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## davey68 (Oct 16, 2013)

Will any check engine light ever come on?


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## Lotek (Apr 24, 2013)

davey68 said:


> Will any check engine light ever come on?


No, not a driveability issue. ABS/TCS ligght will come on eventually, but if you can duplicate the concern, it should be fairly easy to isolate the wheel with a scantool during a roadtest.


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## 47_47 (Sep 11, 2007)

To the op does the ABS light come on and stay on? If your ABS is working correctly, the problem cannot be a wheel speed sensor or wiring to the sensor.

probable causes (in order):
worn front tires 
hard acceleration causing slip
bad tcm / bcm


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## cjm94 (Sep 25, 2011)

47_47 said:


> To the op does the ABS light come on and stay on? If your ABS is working correctly, the problem cannot be a wheel speed sensor or wiring to the sensor. probable causes (in order): worn front tires hard acceleration causing slip bad tcm / bcm[/QUOTE.
> 
> Incorrect a bad wheel wheel speed sensor that only drops out at slow speeds will cause this and is very common. I see a couple a month.


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