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ABS sensor voltage - odd ball


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#1 HONDALEO

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Posted 20 July 2019 - 08:53 PM

I have the ABS kickback on my pedal at about 1 second before coming to a standstill.

 

I am presuming some wheel speed sensor is outputting  a low signal.

 

The official manual gives voltage levels to be expected for the two front wheels speed sensors, and the rear left speed sensor, during spinning the wheel by hand at 1 rev per second.

 

Then for rear right, they state a voltage for that wheel sensor when the wheel is stopped. ??

 

I thought this was a typing error, so I set about measuring all 4 wheel sensor outputs.

 

 

 

The front two were about a +0.50V / -0.50V volts sinewave.

 

This is a bit higher than the specificaion, but I was spinning the front wheels at twice the specified speed, so I think these seem ok.

 

 

Rear Left was +0.2V / -0.3V at about 5 revolutions per second (you can see there's an offset with this one).

 

However, the rear right was +1.9V / -1.9V at about 5 revolutions per second, so this wheel really is an odd ball.

 

 

Does anyone have any idea why this one wheel has a different behaviour to the others?

 

(I must confess I did not check any of these sensors with respect to body ground, but simply back-probed the two sensor wires while they were still in circuit. So obviously before I spun the rear right, the voltage level was 0.0, since it wasn't measured with respect to the body ground, hence I wouldn't be measuring any voltage bias in the way I had it probed).

 

P.S. the reason for the different test speeds was because I tested the front wheels with the car idling in first gear with the car jacked up.

 

I used a cordless hand drill to spins the rears.


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#2 HONDALEO

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Posted 21 July 2019 - 03:23 PM

hmmm..

 

I got this fixed.

 

I made a bar to turn the hub by hand at the recommended speed for testing, and it became clear that the rear left WSS was producing a small signal.

 

I removed the sensor and filed some plastic off the side of it, to allow it to get closer to the reluctor, and now it fine.

 

It turns out that the 1.9V signal dropped right down to the specified level once I turned the hub at 1 rev/second.

 

There is about 130mv bias on the signal side of the sensor with the ignition on, on both rear wheel speed sensors.

 

I din't test the fronts.

 

So that part in the manual about there being a 2.5V presnrt with the wheel stopped seems to be a misprint?

 

Here it is

 

9v8fu9.jpg


Edited by HONDALEO, 21 July 2019 - 03:26 PM.