'05 ABS rear sensor fail

[daviddowns2000]

About a year or so ago I ended up having to replace my ABS hydraulic unit. Everything was working fine until recently when the ABS malfunction light came on, stayed on. Following the diagnostic steps in FSM, checked the error signal with jumper/voltmeter, found error code 16 indicating rear sensor failure. Checked resistance of sensor connector, found infinite resistance. So, I'm assuming the sensor is bad and have ordered a replacement.

My questions are: 1) Is there anything I'm overlooking? 2) Have others here had sensor failure? 3) Why does my ABS hate me? 4) Did Ionbeam ever necropsy the hydraulic unit I sent him?

 

[Queensland Ken]

I think the transducers are a Hall Effect, different to the later models.

Either way I couldn't see one failing.

Could well be an open circuit (infinite resistance) on the wires, ie a broken wire.

Did you measure it at the ABS ecu plug or is there a connector between it and the sensor ??

 

[mcatrophy]

At least on the Gen II, the sensor and its wire is fairly vulnerable during wheel removal/replacment. Could it have been damaged during a tyre change?

 

[3dogs]

Check the wiring diagram--if the sensor has 3 wires--it's a Hall Effect switch/sensor. If it has only 2 wires, it's an AC pickup coil type of sensor. I'm pretty sure it's the AC PU coil type. Check the cable from the ABS unit to the sensor. If it's damaged (wire broken) it can be repaired with no adverse effect on sensor operation--lots cheaper than a new sensor!!!

 

[Constant Mesh]

It's a simple two wire sensor. It's a permanent magnet with fine wire coiled around it.

Using an ohmmeter you should read between 1120 & 1680 ohms looking back into the sensor wires at the disconnect coupler. This coupler is located near the ABS unit under the seat behind the side panel. Must be very small wire and a lot of it to have that much resistance.

One of the two wires is broken somewhere, probably at/near the sensor since it's moved each time the wheel is removed.

 

[daviddowns2000]

It's a simple two wire sensor. It's a permanent magnet with fine wire coiled around it.
Using an ohmmeter you should read between 1120 & 1680 ohms looking back into the sensor wires at the disconnect coupler. This coupler is located near the ABS unit under the seat behind the side panel. Must be very small wire and a lot of it to have that much resistance.

One of the two wires is broken somewhere, probably at/near the sensor since it's moved each time the wheel is removed.

I agree. Like I said, the error code was 16 and my ohmmeter showed infinity at the connector terminals (I even stripped the wires a little, just to be sure to get a solid contact for the meter leads) so I ordered a new sensor. Just wanted to make sure there wasn't something obvious that I might have missed.

I've always been careful with the sensor when changing tires, but my last tire change was done at a dealership because I had an un-pluggable rear flat on the way home from a trip, the only time anyone other than myself has removed a wheel. It's possible that the tech buggered up the sensor's wiring somehow, like by trying to disconnect the wire from the sensor housing instead of removing the whole assembly or some other misstep, but it worked for several months afterwards and I haven't pulled the wheel in that time, so I really have no reason to blame the shop...they were actually extremely helpful and fair (RideNow Powersports in Ocala, FL.), stayed after closing time to wait for the tow truck to bring me in, got me back on the road that night with a new tire from their inventory and didn't overcharge on tire or labor.

Anyway, the diagnosis points to the sensor and I will be overjoyed if replacing it does the trick, unlike most of my attempts when the solution seems so straightforward.

 

[leedavis]

I've had to replace both the hydraulic block and the rear sensor over time on my 04. You're not alone - it happens.

 

[Roger55]

I seem to have the opposite problem. I recently hit my brakes pretty hard at a light change. My rear brake locked up. I'm thinking that's not supposed to happen (I have tried my rear anti-lock before in a more controlled situation and they worked fine "click-click-click"). I tried it again approaching a stop sign on the way to work, same result, rear wheel locked up. So I put it up on the center stand, started it up and put it in gear. ABS light lit up just as it is supposed to do right (front wheel not moving, rear wheel spinning)? I'm guessing I need to replace the hydraulic unit ($$$$). Any suggestions?

 

[juniorfjr]

I seem to have the opposite problem. I recently hit my brakes pretty hard at a light change. My rear brake locked up. I'm thinking that's not supposed to happen (I have tried my rear anti-lock before in a more controlled situation and they worked fine "click-click-click"). I tried it again approaching a stop sign on the way to work, same result, rear wheel locked up. So I put it up on the center stand, started it up and put it in gear. ABS light lit up just as it is supposed to do right (front wheel not moving, rear wheel spinning)? I'm guessing I need to replace the hydraulic unit ($$$$). Any suggestions?

I'm having the same problem. Flushed a lot of brake fluid through the system and still locks up. Probably won't replace the hydraulic unit because of cost. Through about running some trans fluid thru it to see if it'd free it up. Used to free a stuck lifter that way.

 

[daviddowns2000]

I seem to have the opposite problem. I recently hit my brakes pretty hard at a light change. My rear brake locked up. I'm thinking that's not supposed to happen (I have tried my rear anti-lock before in a more controlled situation and they worked fine "click-click-click"). I tried it again approaching a stop sign on the way to work, same result, rear wheel locked up. So I put it up on the center stand, started it up and put it in gear. ABS light lit up just as it is supposed to do right (front wheel not moving, rear wheel spinning)? I'm guessing I need to replace the hydraulic unit ($$$$). Any suggestions?

Sounds familiar. Search the forum for "hydraulic unit", there are several threads (start here: https://www.fjrforum.com/forum//index.php/topic/136822-rear-abs-not-working-abs-light-not-coming-on/ and here: https://www.fjrforum.com/forum//index.php?showtopic=135478&&gopid=915253&&page=5&do=findComment&comment=915253). Chances are good that if the system fails without the ABS malfunction light or error code signal (see Ionbeam's posts in the above-cited threads as well as the service manual for detection procedure), it is the hydraulic unit.

I found a salvage unit on the internet for a fraction of what a new one costs, installation is fairly straightforward. Make sure the model year is the right one, IIRC, they differ.

Yamaha views out-of-warranty hydraulic unit failure as a "wear item" so don't expect any consideration from them.

 

[wmadoty]

Don't put anything in where brake fluid goes but brake fluid. You will be replacing parts for a long time if you put that tranny fluid in there. The oil reacts with the rubber parts and distorts them.

 

[ionbeam]

Don't put anything in where brake fluid goes but brake fluid. You will be replacing parts for a long time if you put that tranny fluid in there. The oil reacts with the rubber parts and distorts them.

While brake fluid and transmission fluid are both a form of hydraulic fluid, it's all the extra additives that the transmission fluid is fortified with that your brake system doesn't want to ingest, starting with the seal swelling ability.

 

[mcatrophy]

I seem to have the opposite problem. I recently hit my brakes pretty hard at a light change. My rear brake locked up. I'm thinking that's not supposed to happen (I have tried my rear anti-lock before in a more controlled situation and they worked fine "click-click-click"). I tried it again approaching a stop sign on the way to work, same result, rear wheel locked up. So I put it up on the center stand, started it up and put it in gear. ABS light lit up just as it is supposed to do right (front wheel not moving, rear wheel spinning)? I'm guessing I need to replace the hydraulic unit ($$$$). Any suggestions?

If your speed was below about 5mph(?), the ABS will not operate, the wheel can lock. This is the designed operation. Same at the front, beware gravelly hard stops with the front brake!

 

[ionbeam]

If your speed was below about 5mph(?), the ABS will not operate, the wheel can lock. This is the designed operation. Same at the front, beware gravelly hard stops with the front brake!

Yamaha claims that below 7 mph the ABS will not operate. How would you feel if the ABS prevented your wheels from ever locking up? I'm thinking that if you have your ABS active and you are nearing a stop and the ABS prevents your wheels from coming to a complete stop you ain't gonna stop, ever

 

[RadioHowie]

Sounds to me like another Gen I ABS pump failure.

Welcome to the Club!

 

[daviddowns2000]

Sounds to me like another Gen I ABS pump failure.
Welcome to the Club!

Did you ever get yours fixed?

 

[RadioHowie]

Nope! I simply remain aware the ABS is FUBAR and NEVER, EVER knowingly put myself in a situation where panic-stopping is an option.

However, the (unfortunately) many panic-stop situations forced upon my by brain-dead cagers has taught me well how to "go with the slide" and prevent high/lowsides.

Does make life interesting...I must say that!

 

[juniorfjr]

Nope! I simply remain aware the ABS is FUBAR and NEVER, EVER knowingly put myself in a situation where panic-stopping is an option.
However, the (unfortunately) many panic-stop situations forced upon my by brain-dead cagers has taught me well how to "go with the slide" and prevent high/lowsides.

Does make life interesting...I must say that!

That's my plan for the time being. I've been riding a year without the abs and have learned how to ride a bike without it again. I'm assuming that it's no diff than a non abs now.

 

[RadioHowie]

Except for the extra 10/15 pounds of useless weight it's carrying.