'07 4runner - how does speed sensor work?

[NCFisher]

I'd purchased the Koyo LR wheel bearing assembly 3rd party for dealer to install. Now, the VSC & ABS lights stay on. Dealer says it's because the sensor in the wheel bearing is bad.

Is the dealer correct (that there's a sensor inside the bearing hub assembly) or does the sensor get a reading elsewhere ? I know Gen3 had a tone ring with a magnetic tooth, but have been unable to find how Gen4 works.
Thank you.

 

[cabowally]

The sensor is attached to the steering knuckle with one bolt. There is a hole where the sensor tip sits in the knuckle but the sensor is not "in" the wheel bearing.

Often after work is done to the front end clearing and doing a zero point calibration is necessary. That could be an issue.

FROM THE FSM (get it from the sticky)

DESCRIPTION
The speed sensor detects wheel speed and sends the appropriate signals to the ECU. These signals are used to control the ABS, BA, TRAC, A-TRAC, VSC, AUTO LSD, downhill assist and hill-start assist control systems. This speed sensor contains a sensor IC, which consists of 2 MREs (Magnetic Resistance Element). The speed sensor rotor, which consists of 48 sets of N and S poles that are arranged in a circle, is integrated with the inner race of the hub bearing.
To detect the rotation direction, the output waves are used to determine the relationship of the pulses that are generated by 2 MREs. Upon receiving this signal, the sensor IC outputs a forward or backward wave to the ECU.

A faulty sensor should be throwing a C0200 DTC.

First thing I'd do is to start with making sure the gass cap is secure, disconnect the neg battery wire and see what happens.

 

[NCFisher]

Thanks for the greatly detailed response, Cabowally. That points me to the problem, have a good one!

 

[NJshadow93]

I would say that whoever did the install damaged the sensor. It's not hard to damage it if you're not careful. I replaced both hub bearing assemblies myself and did not touch the sensor or require a zero point calibration. That is one of the risks when doing that job since, as mentioned, it's only secured with one bolt.

 

[NCFisher]

Unfortunately it's left rear bearing which I can't DIY. I had the dealer order Toy parts yesterday and just get it fixed. I can't see the sensor rotor - a magnetic ring - being bad; it may be the supplier didn't press the rotor into the assembly. When I have the Koyo part back in hand, any way to test it or visually verify? I am no mechanic.

 

[BlackWorksInc]

Gas caps do not fix Traction control problems... just saying...

The tone rings are built into the bearings on many new vehicles and they are actually directional, in the sense that if installed backwards the tone ring isn't where its supposed to be. I doubt the tone ring went bad, its not impossible but unlikely. The sensor itself is bolted into the spindle of backing plate, was the bearing replaced before this problem happened or are you replacing it again because this occurred?

Did the dealer give you any DTCs when they checked the system or did they not note it down the RO?

 

[NCFisher]

The alleged OEM Koyo part was faulty. I appreciate all the replies.