ABS2 issue

Hi,

I am working on a friends bike, a R1100RT, '97. The ABS lights would flash alternatively when the bike came in. The battery on the bike is not great, that's for sure, it starts the motor with some difficulty.

Now for the ABS... I cannot reset it unless the engine is running at idle.. I did the relay mod and also added a button to bypass the relay, in case I need to (I usually mount the relay under the tank, next to the ABS unit).

Once reset, the lights flash normally, together. I take off and hear the ka-plung sound of the unit, all normal so far. But then, after rolling a few more meters, the lights start to flash in error mode again...

I don't have the ABS adapter module for my GS911 since I traded my old unit for the new wifi one.

I guess it is the unit fault, one of the pistons under the bleeders in the unit getting stuck and not lowering fast enough. Also, another weird thing, there seems to be no pressure in the rear brake after the ka-plung, the pedal looks like it goes all the way down, freely.

Any other ideas I can try before swapping the ABS unit? I have measured the clearance/sensor gap, replaced the rear sensor, nothing changes. I do have a front side sensor I can swap if needed.

Dan.

Hi,

 

I am working on a friends bike, a R1100RT, '97. The ABS lights would flash alternatively when the bike came in. The battery on the bike is not great, that's for sure, it starts the motor with some difficulty.

Now for the ABS... I cannot reset it unless the engine is running at idle.. I did the relay mod and also added a button to bypass the relay, in case I need to (I usually mount the relay under the tank, next to the ABS unit).

Once reset, the lights flash normally, together. I take off and hear the ka-plung sound of the unit, all normal so far. But then, after rolling a few more meters, the lights start to flash in error mode again...

 

I don't have the ABS adapter module for my GS911 since I traded my old unit for the new wifi one.

 

I guess it is the unit fault, one of the pistons under the bleeders in the unit getting stuck and not lowering fast enough. Also, another weird thing, there seems to be no pressure in the rear brake after the ka-plung, the pedal looks like it goes all the way down, freely.

 

Any other ideas I can try before swapping the ABS unit? I have measured the clearance/sensor gap, replaced the rear sensor, nothing changes. I do have a front side sensor I can swap if needed.

 

Dan.

Morning Dan

With the rear having no pressure and/or the pedal moving to a different pressure point that sort of points to an internal fluid volume problem (a stuck or sticking piston comes to mind). Or possibly an internal chain problem.

With a bad wheel speed sensor you get the failure lights after ride-off but no change in normal service brake function, just no ABS ability.

So there is nothing I can do for the stuck piston issue, right? Except for replacing the whole unit with a fully functioning one...

Dan.

So there is nothing I can do for the stuck piston issue, right? Except for replacing the whole unit with a fully functioning one...

 

Dan.

Morning Dan

There might be some things that you can do.

The first would be to disassemble the ABS unit & free up, clean up, loosen up the stuck piston (I haven't seen any one doing that in years now as functioning used ABS controllers are fairly cheap on E-Bay now) -- At least in the USA here.

Another way is to install fresh brake fluid then keep fooling with it to see if you can make it work. If you can get it working (even a little, or once in a while) then take the bike on a dirt road & force it to enter ABS mode on the offending end. Sometimes just exercising the ABS unit with fresh fluid can free up sticking pistons.

If you do manage to get it functional then ride a low traction area daily for a while then force ABS function a few times to exercise the pistons & hopefully keep it freed up.

You might also try forcing the brake pads on the offending end all the way back into the calipers then do some ride-off to see if the volume change will effect piston travel (more hoping than based on fact with this one) .

Forgot to mention that I have already changed the braking fluid.

For removing the piston, I can leave the unit be on the bike, just remove the bleeders, I remember it's a 24 mm wrench, right? A few years have passed since I opened an ABS unit.

Dan.

Cut your losses, Dan and rip the whole sodding thing out to get better, safer, more predictable efficient braking.

I have opened the ABS unit bleeders, removed the parts and pistons in there, there was some thin aluminum powder like stuff on the outer side of the front brake filter, cleaned everything, put it back, bled the brakes and the result was the same...

I am getting the donor ABS unit tomorrow, we'll see how that works.

Dan.

Could be worse, could be a H-D !!!!!

What a testament to doing regular brake fluid changes.........fluid is a very cheap item to buy and how bloody difficult is it to R&R brake fluid on most bikes?

Ok, iABS is more of a PITA but still very doable !

Update:

I have received the donor unit, from a R850RT. I swapped the brain from the 1100 to the 850 unit, fitted it, bled the brakes, reset the ABS and it fails just as before...

The donor unit came with it's own relay, if that matters.

After the first reset, something weird happened, it seemed to make a couple of ka-plungs while riding at slow speed then it started to flash in error mode.

So now I have a donor abs unit, a donor rear abs sensor and the only thing left unchanged was the front ABS sensor.

I took the front sensor off my RT and replace it. After resetting the abs, when switching the ignition on, it blinks in error mode before switching the engine on, with the donor abs sensors. With it's own sensor, the dash flashes as usual, and it shows the error after riding a couple of meters.

My conclusion is that the unit itself is fine, at least the motor and hydraulics. I am not sure about it's brain, though.

Also, does the brain test the sensors before rolling? Why does it not accept the front donor sensors? Are there more than one kind?

It's almost as if something vibrating triggers the error. I will try to put in a new battery and open the starter motor for inspection tomorrow, first thing, before other tests...

Dan.

Update:

 

I have received the donor unit, from a R850RT. I swapped the brain from the 1100 to the 850 unit, fitted it, bled the brakes, reset the ABS and it fails just as before...

The donor unit came with it's own relay, if that matters.

After the first reset, something weird happened, it seemed to make a couple of ka-plungs while riding at slow speed then it started to flash in error mode.

So now I have a donor abs unit, a donor rear abs sensor and the only thing left unchanged was the front ABS sensor.

 

I took the front sensor off my RT and replace it. After resetting the abs, when switching the ignition on, it blinks in error mode before switching the engine on, with the donor abs sensors. With it's own sensor, the dash flashes as usual, and it shows the error after riding a couple of meters.

 

My conclusion is that the unit itself is fine, at least the motor and hydraulics. I am not sure about it's brain, though.

Also, does the brain test the sensors before rolling? Why does it not accept the front donor sensors? Are there more than one kind?

 

It's almost as if something vibrating triggers the error. I will try to put in a new battery and open the starter motor for inspection tomorrow, first thing, before other tests...

 

Dan.

Afternoon Dan

With all that your have changed & swapped there is no way to know exactly what your are dealing with. You either have a basic bike problem (open or shorted wheel sensor or open or shorted wheel sensor wiring.

Or, you have a basic problem with the ABS unit or a mis-match of brain to hydro unit.

If you suspect a wheel sensor then unplug the main harness at the ABS unit & ohm out the front & rear wheel sensor circuits (front & rear should ohm out close to the same.

If resistance is OK then put your meter on AC voltage & test sensor output at ABS unit connector by spinning each wheel (should be close to same AC voltage output from both front & rear with wheel spinning the same speeds)

How would one usually test an ABS sensor? By resistance or by voltage? Any values I can reference to?

Dan.

How would one usually test an ABS sensor? By resistance or by voltage? Any values I can reference to?

 

Dan.

Afternoon Dan

Either or preferably both.

I have some resistance measurements somewhere but I'm not near them until next week.

Voltage measurements are not that precise as you have both wheel spin speed & meter load that effects them so you are basically just looking for a front/rear matching output.

You have a basic comparison right on the bike for both resistance & voltage output, just use the other end. (you are basically looking for an open or a short, or real low voltage output.

Sorry if stating the obvious but isn't low battery voltage a known cause for ABS2 error condition? This appears to be more involved but removing low bsttery out of the equation may help the troubleshooting.

Sorry if stating the obvious but isn't low battery voltage a known cause for ABS2 error condition? This appears to be more involved but removing low bsttery out of the equation may help the troubleshooting.

Afternoon kalali

That is usually the cause BUT, Dan has done the relay modification so the ABS doesn't run it's checks UNTIL the engine is started & the alternator is producing power.

The other thing is, the system is faulting at a different time than it would if it was due to a low battery voltage.

Turns out it was not the battery. I swapped a good, maintenance free one, from my GS project, that is know to be good, and the result is the same.

What I do not understand, is why the brain only accepts the front sensor that was on the bike originally... I have measured them and they all seem to have the same value, ~ 130 ohms if I remember correctly.

Bought an analog voltmeter to read the error codes, but it flashes at the same freq as the lights in the dash, so error reading is not an option, for some reason. The same voltmeter put on my RT that has the front sensor disconnected flashes 3 times, the correct error for faulty front sensor.

Another test I did was hooking the original ABS unit having the 850RT brain to the harness, the lights in the dash flash at the same rate.

One thing left to do. I noticed that the starter motor has the two 8 mm nuts on the back, altered, so someone must have worked on it, perhaps that is the issue. Will get into it tomorrow evening, I really hope that is the problem, because now I have changed the ABS unit, the sensors, everything, without any luck...

Dan.

Very disappointed... Fixed the starter motor, the issue remains...

One thing I noticed, after resetting, just getting the bike off the centerstand triggers the error.

So I reset it again while the bike was on it's wheels and pressed the front brake and rocked it back and forth, while the wheels were not spinning, and the error re-appeared.

It was getting late and tomorrow, I think I will check the wiring harness for battery acid leaking on it, like it happened to @GSaddict ?

Dan.

I was convinced I got the bike fixed last night...

When testing the bike, at all times, I was running the ABS trough the relay I mounted previously (the relay job was the first thing I did to the bike after resetting the errors). I think the relay is not trustfully so I read that I don't really need it.

Turns out the pin 15 on the ABS connector only triggers voltage supply to the unit (figured it before as there are 2 thick wires in there too) and you can just connect the alternator blue wire to the pin in the connector, which I did. I switched the ignition on, measured 12V on the other relay wire, isolated it with heat shrink tubing and connected the alternator wire to the pin 15, using a 7.5A fuse. I figured it's a good idea to put the fuse in there.

When switching the bike on, the error was still there, only this time, I was able to read the error using the analog voltmeter I got last weekend. 3 blips, pointing to the front sensor. So I switched the bike's sensor to the one that previously it did not want to accept, and it seemed to work! ABS ka-plungs and then it kicks in whenever needed!

I took off the front fender and wheel and permanently installed the donor sensor but when the job was done... the error was back again.

Looks like GS Addict is on the money, the issue seems to be at the connector level. I remember another bike having the same issue like this one that got fixed by fiddling the connector.

Should I just cut it out and solder the wires?

Dan.

Congrats to you Dan for your dogged perseverance with this ABS issue. I can only assume that having ABS is very important to you. I know how much of a benefit it is in a difficult braking scenario, especially in the wet or on grass. In the past, I've had five different Beemers with ABS and can count on the fingers of one toe the occasions when the system has rescued me from a sticky situation where a sleepy cager pulls out of a side road and T-bones a biker.

Both my bikes now are non-ABS so I just ride accordingly and always favour the rear brake on the rare occasions whenever I need to slow down in haste.

As I mentioned earlier - cut your losses and rip the lot out.

I was convinced I got the bike fixed last night...

When testing the bike, at all times, I was running the ABS trough the relay I mounted previously (the relay job was the first thing I did to the bike after resetting the errors). I think the relay is not trustfully so I read that I don't really need it.

 

Turns out the pin 15 on the ABS connector only triggers voltage supply to the unit (figured it before as there are 2 thick wires in there too) and you can just connect the alternator blue wire to the pin in the connector, which I did. I switched the ignition on, measured 12V on the other relay wire, isolated it with heat shrink tubing and connected the alternator wire to the pin 15, using a 7.5A fuse. I figured it's a good idea to put the fuse in there.

 

When switching the bike on, the error was still there, only this time, I was able to read the error using the analog voltmeter I got last weekend. 3 blips, pointing to the front sensor. So I switched the bike's sensor to the one that previously it did not want to accept, and it seemed to work! ABS ka-plungs and then it kicks in whenever needed!

I took off the front fender and wheel and permanently installed the donor sensor but when the job was done... the error was back again.

 

Looks like GS Addict is on the money, the issue seems to be at the connector level. I remember another bike having the same issue like this one that got fixed by fiddling the connector.

Should I just cut it out and solder the wires?

 

Dan.

Morning Dan

It's not a good idea to run the ABS ignition circuit directly from the alternator blue wire. It will work (sort of) but places a great load on the alternator voltage regulator on a circuit that isn't designed to handle that load. It will also place an additional load on the generator light circuit & that delays start of charge.

If you don't want to add another working relay then you might eliminate the blue wire going to the ABS entirely, then simply reconnect the green wire from the ignition circuit (back to stock) but install a N/C push button switch in that green wire.

With a N/C push button you have stock ABS ignition circuit that will power the ABS electronics at key-on. For most usage that works just great. On the occasional occurrence of a low battery at key-on you can start the engine & once running push the push button to reset the ABS at full system (charging) voltage.

On your wheel speed sensor connector failure-- If you are sure that the connector, or the terminals in the connector, are the root of your problem then you could wire directly but that is a bubba repair. Why not do it correctly & either find & repair the problem area, or at least install a new waterproof connector & terminals (a sealed 2 terminal weather pack makes a great 2 wire repair connector) not stock but will work fine. (check E-Bay for sealed weather pack connectors).

If you do choose to eliminate the wheel speed connector then either use an approved ABS repair (sealed) repair splices or make sure that your repair is sealed & totally water/weatherproof.

So the R1100RT bike is fully functional now, everything works fine, it is reliable.

I am working on a R1150RT, servo brakes, it has about the same issue. GS911 pointed towards the front sensor as defective, so I traced the wires and it looks like the wire was rubbing on the aluminum fork, till it got to the copper.

I have replaced the sensor, but the error is the same! Measured the resistance of the sensor at the connector level, R/H side of the bike, near the oil cooler, and it is OK, 130 ohms.

So the issue must be somewhere in the harness, between the ABS connector and the unit's connector.

Can someone point me towards a 1150Rt wiring diagram for the ABS or point me what pin numbers correspond to the front ABS sensor in the large unit connector? I remember I saw some electrical diagrams in my Haynes manual, but can't remember if applicable to my bike...

Dan.

So the R1100RT bike is fully functional now, everything works fine, it is reliable.

 

I am working on a R1150RT, servo brakes, it has about the same issue. GS911 pointed towards the front sensor as defective, so I traced the wires and it looks like the wire was rubbing on the aluminum fork, till it got to the copper.

I have replaced the sensor, but the error is the same! Measured the resistance of the sensor at the connector level, R/H side of the bike, near the oil cooler, and it is OK, 130 ohms.

So the issue must be somewhere in the harness, between the ABS connector and the unit's connector.

Can someone point me towards a 1150Rt wiring diagram for the ABS or point me what pin numbers correspond to the front ABS sensor in the large unit connector? I remember I saw some electrical diagrams in my Haynes manual, but can't remember if applicable to my bike...

 

Dan.

Morning Dan

2 wires involved-- yellow/red & yellow/brown.

The yellow/red enters the ABS controller (ABS pump) on pin 33 & the yellow/brown enters the ABS controller on pin 35.

No other in-line connectors between the wheel speed sensor pigtail connector & the ABS controller.

I looked these wire colors & pin numbers up in my European BMW 1150RT wiring manual.

Right... I should just have searched this on google...

http://www.mac-pac.org/wp-content/uploads/2014/09/R1150RT-Electric-Diagram-V3_3.pdf

AFAIK, ABS sensors do not have a polarity, right? does it matter to the ABS unit which wire goes where?

Dan.

I was able to verify that the wires are not interrupted between the ABS sensor connector and the unit connector.

Took off the unit and opened the brain, there seems to be no burnt parts in there. Will take it to someone that is able to verify it.

Dan.

 

 

 

AFAIK, ABS sensors do not have a polarity, right? does it matter to the ABS unit which wire goes where?

 

Dan.

Morning Dan

I'm not sure, it might?

The yellow/red is the high (+) & the yellow/brown is the low (-).

On the wheel speed sensor pig tail itself terminal #2 is the (+) & terminal #1 is the (-).

Also make sure that the front wheel has the correct tone ring for the I-ABS system & that no damage to any of the tone ring slots.

I was trying to fit the older sensor from a k1100 to the 11500... So there are two types and the sensors are not interchange-able.

Fitted the correct sensor and now there are no more errors. Opened the bike for a clutch change and will see how it works out after the tail is dropped back down.

Dan.