Wheel sensors

[The Gecko_imp]

After I solved my ABS (bleeding) problems last year - not entirely painless - today I start trusting in those people who say ABS is just another pain on a m/c. Here is why:

My ABS light goes off after launch, but then comes on, every now and then ... 5-10-20 miles. Sometimes it goes off after a while. Sometimes one has to toggle the ignition key. Guess, sound like a sensor problem to me, in particular since the baby has seen a lot of dirt in the last few weeks. Alrighty, I clean everything - doesn't help.

So I check the SM, it says wheel sensors cannot be adjusted, "make sure nothing is bent". Thank you. Value should be 0.02 - 0.05 in, and so I check. Front is straight, clean and looking good, with 0.03 in. Next back, everything is un-bent, clean, straight and looking good. And I read 0,01 in. I see nothing which could explain the unexpectedly small gap. Spinning the wheel - same result everywhere.

Could this explain my light coming on ? I'd rather not bring all those greenbacks and ask the dealer.

[pekingduck]

If the clearance is half of the minimum spec, then it surely could be the problem. For more clearance, undo the 2 bolts and space the speed sensor outward from the caliper bracket with shims or thin washers.

[max]

Can i just say that it's a pleasure to have you on the forum and explain the various aspects of your bike!

As Pekingduck has mentioned this could be the problem as well as a suspect connector at the end of the abs sensor cable.

Here is a picture of how the system is supposed to work;



As you can see it has a magnet inside the sensor and a coil around a soft steel core ( soft steel does not retain magnetism and reacts to a changing magnetic field ), as the teeth pass the sensor the magnetic strength changes ( it can conduct the magnetic field through the steel ring's " spokes " ) through the soft steel core which changes the magnetic field presented to the coil.

This change happens very quickly ( if you could hear it it would sound like a tone with a varying pitch ( this is how a hammond organ works ) the ecu reads this "tone" and checks for rapid changes in frequency, it makes a decision as to when to release the brake pressure if the brake light is on and prevent the wheel from losing traction.

If the sensor is too far away from the ring the change in intensity is not big enough for the ecu to react and when it is too close it only senses a constant magnetic field with the same malfunction, so it must be in the optimum place.

Here is a link to the article;
https://www.google.com/imgres?imgurl=htt...egUIARD0AQ

So after all that what to do?
There could be some steel dust on or near the sensing ( flat )surface of the sensor, so take it out of it's housing and see if there is any debris on it.

Also the "tone"ring is on the wheel and the sensor is on the hub of the brake assembly, when the tires are changed the gap could change ; https://www.partsfish.com/oemparts/a/hon...ke-caliper

If not do what Peking duck suggested and put some cardboard/paper spacer under the sensor, measure the new gap and see if that eliminates the erratic abs light.

Nice to see the measured gap values, you almost solved the issue i think and i hope we clarified how the system works.

[The Gecko_imp]

Now it's getting interesting. Pulled the sensor out, widened a washer which had a thickness of 0.035 in, put it all back togetherand measured again. Imagine my surprise when the I see no change. Okay, before you laugh, here is the text and the picture from the SM (please Honda, forgive me that copyright violation) :

Measure the clearance (air gap) between the sensor and pulser ring at several points by turning the rear wheel slowly.
[attachment=16831]

What the SM doesn't say, and the picture doesn't show, there is a metal casing (a tube which is part of the brake caliper) protecting the sensor. And when you measure EXACTLY as shown in the pic above, you measure the distance between the pulser ring and that casing. The sensor DOES NOT stick out on the inside of the tube, so there is no way to even measure the required gap. Darn. Adding a washer between sensor and caliper structure does indeed move the sensor towards the outside, but how much, how little is needed ? No idea.

Could be that this casing got introduced with the EX in 2017 (my manual is for the 2013-16 models), cannot find another one.

[pekingduck]

Now it's getting interesting. Pulled the sensor out, widened a washer which had a thickness of 0.035 in, put it all back togetherand measured again. Imagine my surprise when the I see no change. Okay, before you laugh, here is the text and the picture from the SM (please Honda, forgive me that copyright violation) :

Measure the clearance (air gap) between the sensor and pulser ring at several points by turning the rear wheel slowly.
[attachment=16831]

What the SM doesn't say, and the picture doesn't show, there is a metal casing (a tube which is part of the brake caliper) protecting the sensor. And when you measure EXACTLY as shown in the pic above, you measure the distance between the pulser ring and that casing. The sensor DOES NOT stick out on the inside of the tube, so there is no way to even measure the required gap. Darn. Adding a washer between sensor and caliper structure does indeed move the sensor towards the outside, but how much, how little is needed ? No idea.

Could be that this casing got introduced with the EX in 2017 (my manual is for the 2013-16 models), cannot find another one.

Gecko, not sure what tube or obstruction you are encountering. Here is a pic of the 2017 manual page, and a pic of the backside of a 2017 caliper bracket (disregard the lack of sensor bolt holes here).
[attachment=16832][attachment=16833]

[Cormanus]

With apologies to all, the photos of the manual page has had to be removed for reasons of copyright.

[pekingduck]

"If my explanation wasn't clear, let me try again. Both of my sensors sit inside a casing which looks like a tube, but they do not stick out. When you measure which a thickness gauge all you measure is the distance between the end of the casing and the pulser ring - and this is good (but useless) in front, and bad and useless in the rear. When you add washers to the sensor base it moves the sensor out, but you can't measure how much."

Looking at the new picture, I see what you mean by the tube is a raised cast boss, and the sensor end looks like it is close to or more recessed than the boss. So let's re-think this.

The problem came on suddenly/intermittently without doing a tire change or anything, I assume. The reluctor wheel can get bent or damaged pretty easily, so make sure the slotted portion is smooth and even, with no waves or bends.

Problems like this are most often a connection problem, so check the wires for damage or a loose connection. Beyond that, you may have to look for the trouble code (if there is one), but you'll need the 2017 manual for very specific diagnosis instructions.

[The Gecko_imp]

Correct, no tire change, no bent pulser ring, etc.
Next steps is connectors, cannot des etc.
But the mystery remains. How can the manual require to measure the distance,
if the sensor end is flush or recessed?

Thanks for the pics

[1973cb750]

might try an osciliscope i wonder if the sensor is just bad

[pekingduck]

Correct, no tire change, no bent pulser ring, etc.
Next steps is connectors, cannot des etc.
But the mystery remains. How can the manual require to measure the distance,
if the sensor end is flush or recessed?

Thanks for the pics

While we imagine someone writing the manual with a bike to tear down in front of him/her, it is not the case. Not everything is checked - sometimes it is assumed based on previous knowledge. Sometimes they are just plain wrong.