2003 R1150RT - Rear I -Abs out and Flashing Lights ?

ABS Guru's, I need some clarification Please !

I just completed full clutch spline lube. After reassembling the bike I verified that the ABS Servo system was working, brake lights working, servo's sounding off when brakes activated. But I hadn't run a roll-on test yet. I next balanced the throttle bodies. I backed it out for a road test and realized that the rear brake light was not working and the servo system was off.

With or without the engine running, I am seeing a flashing 4 per second brake failure light and a steady general warning light.

I found this on line:

ABS Flashing Light Codes for the 1100s/1150s

1. Gen OFF, ABS ON = Only residual braking in both circuits.
2. Gen OFF, ABS flashes at 1 Hz = ABS not available. Pull-away test not completed.
3. Gen OFF, ABS flashes at 4 Hz = Only residual braking function available in both circuits.
4. Gen ON, ABS off = rear light/brake light defective.
5. Gen ON, ABS flashes at 1 Hz = At least one brake circuit without ABS.
6. Gen ON, ABS flashes at 4 Hz =At least one brake circuit in residual braking function mode.
7. Gen AND ABS flashing alternately at 1 Hz = Fluid level in Integral ABS too low, or Low voltage.

The Gen light is off when the engine is running, on when it's not. Is the above list for engine on or engine Off?

So It looks like the Third Option Above? Or is it the Sixth?

I had a friend come over today with his GS 911 unit. The only thing we could find was bad brake switch warning.

I disconnected the rear switch and used a VOM. I see "0" when pedal relaxed and a "1" when the pedal depressed. So the switch appears to be OK. The bulb lights with the front brake.

I disconnected the battery for an hour and a half then went for a short ride. No change from the Roll-on test, but by the time I got home the front servo was off. I turned the ignition off in the garage and back on and the servo was back. A safety thing I guess. Never got the rear servo going.

Where do I go from here????? I'm kind of stuck!

Thanks
Rod

When was the last time the brake fluid was changed?
I'm not saying that's the cause for certain, but a lot of the bikes with these systems don't get flushed often enough.
Should be done every 2 years IIRC.
It's a bit tedious, but not rocket surgery.

It looks as though it is #6.

jeff488 said:

When was the last time the brake fluid was changed?
I'm not saying that's the cause for certain, but a lot of the bikes with these systems don't get flushed often enough.
Should be done every 2 years IIRC.
It's a bit tedious, but not rocket surgery.

It looks as though it is #6.

Click to expand...

I bought the bike from my local dealer in October. They did a complete flush, full fluid change and annual maintenance.

Trace your wiring. The brake lamp gets it's power from a single output which is controlled by inputs from each brake switch. You should see 12 volts on one lead and some continuity on the other where the brake switch plugs in. I would guess you pinched the wiring somewhere along the way. Even with an ABS failure, you should still have brake lamp function.

deanwoolsey said:

Trace your wiring. The brake lamp gets it's power from a single output which is controlled by inputs from each brake switch. You should see 12 volts on one lead and some continuity on the other where the brake switch plugs in. I would guess you pinched the wiring somewhere along the way. Even with an ABS failure, you should still have brake lamp function.

Click to expand...

With servo brakes the ABS module initiates the brake light. The pedal and lever send a signal to the module of opposite logic. ie: pedal or lever in rest position = circuit closed (opposite logic to ABS II non servo where the lever/pedal directly activates the brake light).

GSAddict said:

With servo brakes the ABS module initiates the brake light. The pedal and lever send a signal to the module of opposite logic. ie: pedal or lever in rest position = circuit closed (opposite logic to ABS II non servo where the lever/pedal directly activates the brake light).

Click to expand...

So, is it normal for the ABS module to not illuminate the brake light if the system is in residual mode? That seems kind of dangerous.

This whole system is new to me, I am struggling to understand what is going on here! I just came off a K1100LT, which seems simple by comparison.

Another question, if the system is in residual mode - what do I do to fix it? How do I trouble shoot it?

Thanks
Rod

I have spent the last day or so studying all of my manuals and scanning other related threads on this forum and I think I understand what is going on better now.

My problem is that the Self-Diagnosis step is failing before I even start the engine.

I do have the original rubber brake lines, don't know if breakdown that could cause these symptoms? I do have residual braking in the rear.

I have gone through checking the reservoir levels on the ABS Unit, all full and clean new fluid.
I have replaced both the tail and stop light bulbs, no change.

I did find something that worries me though. In double checking the work I have done, from my just finished spline lube, I found that the rear brake switch wire had been pinched by a rear master cylinder mounting bolt creating a short on the positive line. Studying Mr. Raymond's excellent schematic I see that this switch connects directly to the ABS Control Unit. I fear a strong possibility that I have damaged the unit. $$$$$$ as it applies to the rear brakes!

What are you folks thoughts?

Thanks
Rod

rkildu said:

I have spent the last day or so studying all of my manuals and scanning other related threads on this forum and I think I understand what is going on better now.

My problem is that the Self-Diagnosis step is failing before I even start the engine.

I do have the original rubber brake lines, don't know if breakdown that could cause these symptoms? I do have residual braking in the rear.

I have gone through checking the reservoir levels on the ABS Unit, all full and clean new fluid.
I have replaced both the tail and stop light bulbs, no change.

I did find something that worries me though. In double checking the work I have done, from my just finished spline lube, I found that the rear brake switch wire had been pinched by a rear master cylinder mounting bolt creating a short on the positive line. Studying Mr. Raymond's excellent schematic I see that this switch connects directly to the ABS Control Unit. I fear a strong possibility that I have damaged the unit. $$$$$$ as it applies to the rear brakes!

What are you folks thoughts?

Thanks
Rod

Click to expand...

First of all replace those rubber lines with ss teflon. They all fail, some by bulging, others by flaking inside and blocking the fluid return from the caliper. Until that is done I would not blame the Hydro unit.
Flush with copious amounts of fresh fluid.
As far as the pinched wire goes, I believe that those circuits are internally protected (I could be wrong), they are low level signals (SEH+ #34 And SEHA #36)
When you have fixed, reset the Unit with your friends GS911.
I am confident you will be pleasantly surprised.

rkildu said:

ABS Guru's, I need some clarification Please !...I just completed full clutch spline lube.

Click to expand...

This means that the rear frame was rotated fully upwards and the 11-year old wiring harness was wiggled and flexed. Intermittent shorts or opens are possible, and likely to be weather-dependent. If you're lucky wiggle-testing the harness may cause the ABS fault to come and go.

With or without the engine running, I am seeing a flashing 4 per second brake failure light and a steady general warning light.

Click to expand...

The engine should have nothing to do with the iABS brakes. You can even test the iABS system with the gas tank off; just turn on the key and roll the bike forward. If the engine has any effect I would suspect it is vibrating an intermittent connection.

I had a friend come over today with his GS 911 unit. The only thing we could find was bad brake switch warning.

Click to expand...

GS 911 reports brake switch (or associated wiring) fault, good clue

.. by the time I got home the front servo was off. I turned the ignition off in the garage and back on and the servo was back. A safety thing I guess. Never got the rear servo going.

Click to expand...

For clarification, there is only one servo, aka ABS pump. You mean the front lever actuates ABS brakes but not the rear lever. [Edit by DR on 7/2/2014: Previous was incorrect. There are front and rear servo motor/pumps. In early iABS bikes (up to 2002 at least) either lever operates both servos, normally.]

Other clarifications:
The front and rear brake switches on iABS bikes are NCC configured, or Normally Closed Contact. That is, the circuit breaks when you activate a brake lever. This is a safety feature. Once the iABS is operating, any momentary break of either brake switch circuit (such as unplugging the brake switch connector for example) will activate the ABS pump and the brake light. This will not perform any braking action, unless you also squeeze the lever. [Edit by DR on 8/19/2014: removed a sentence here that wrongly said the iABS Module does not know or care which brake switch was activated]

As noted by others, the iABS Module is pretty rugged and the brake switch inputs should tolerate a short to ground or power. So there is a good chance there is no damage.

Since your iABS works some of the time, you have an intermittent short or open, probably in the rear brake switch circuit, and the fault is seen before the iABS completes initialization.

I wish you happy wiggle testing. No need to run the engine.

PS:
I intend to update soon my R1150RT diagrams that you used, to show the NCC contacts clearly.

Be sure the pinched wire you found is not broken inside.

GSAddict said:

Be sure the pinched wire you found is not broken inside.

Click to expand...

It wasn't broken, but some of the strands were severed. I cut the bad part out and spliced in a short section to repair. I have replacement switch assembly on order from Beemer Boneyard, just got shipping verification.

Doug,

That road test was before I found the pinched wire. I haven't had it out since.

There is a local shop owned by a club member and BMW Rider. He has the shop version of the GS911. I am going there next week to see what it finds. Hopefully he can reset the ABS faults?

Thanks
Rod

rkildu said:

It wasn't broken, but some of the strands were severed. I cut the bad part out and spliced in a short section to repair. I have replacement switch assembly on order from Beemer Boneyard, just got shipping verification.

Doug,

That road test was before I found the pinched wire. I haven't had it out since.

There is a local shop owned by a club member and BMW Rider. He has the shop version of the GS911. I am going there next week to see what it finds. Hopefully he can reset the ABS faults?

Thanks
Rod

Click to expand...

The iABS units are not like other ABS units. The unit resets and does a power on test every time power is applied. The fault you have is not a fault that is stored in the computer. It's a fault the unit has determined exists after power on. Resetting the fault with the GS911 or other diagnostic equipment will have no effect. I have to also agree with the other posters, it seems to be a wiring issue. Have you inspected the main connector on the unit and checked for bent or pushed in pins?

hope this helps,
Paul

Blacque Jacque Shellacque said:

The iABS units are not like other ABS units. The unit resets and does a power on test every time power is applied. The fault you have is not a fault that is stored in the computer. It's a fault the unit has determined exists after power on. Resetting the fault with the GS911 or other diagnostic equipment will have no effect. I have to also agree with the other posters, it seems to be a wiring issue. Have you inspected the main connector on the unit and checked for bent or pushed in pins?

hope this helps,
Paul

Click to expand...

Well my reason to take it to the shop was to find out what error codes were showing and hoping it could be reset. But based on your comments I have decided to do something else.

As I stated above I have a replacement stock switch on the way. The wire in the one I repaired does have another pinched spot but it wasn't broken through so I assumed it was OK. I am going to perform a little more surgery on it tomorrow and cut out most of the wire and all of the bad looking spots and rewire the whole thing. The connectors seem fine. It won't be pretty but it should be all good wire. Then I will see what happens.

Thanks for all the advice
Rod

I found another badly pinched section of the rear brake switch wire!

I cut about 4 inches of questionable wire out of the line and carefully spliced in a new section and reinstalled it.

Switch on and successful initialization! I just got back from a short test ride and everything is operating normally. I guess I won't throw the bike off of a cliff after all.

If you all haven't figured it out yet, I am electrically challenged! It's all smoke, magic and mirrors to me. Except when I see the smoke I know I'm in trouble.

Many thanks to all of you for your patient assistance.

Rod

Every electrical component operates on Smoke.
When you release the smoke, it no longer works.

Congrats on your find!

Another adventure with the rear $ervo.

Finished up a alternator mod and clutch replacement on the ol' pig recently. After reassembling the bike and the brake system I proceeded to bleed said system using a vacuum bleeder on the four circuits as the battery was not yet installed. Imagine my horror upon testing the brake system with the battery in place and having no rear $ervo and experiencing the continuous 4Hz ABS light. Mercy! After another bleed hoping that I had screwed up the process I started to get... concerned... read that as excited.

While diagnosing the problem I removed the connector at the ABS unit so I could meter the footbrake microswitch (pins 7 and 41) to ensure that it operated. It did, or rather, it appeared to. I observed that the microswitch is normally closed when the footbrake lever is up, and opens the circuit when the footbrake lever is pressed to activate the rear brake servo. Hmmm.

Upon researching relevant information on the web I stumbled across this thread and after losing about three hour's sleep the next morning obsessing about the problem I wondered if the servo's active line could be grounded, just as the microswitch does, preventing the servo unit from initializing or activating the rear brake circuit. I metered both wires to ground and found that...

Sure enough, during reassembly of the bike, one of the two wires in the footbrake switch harness (the active wire, of course) had been pinched between the transmission and the RH 'footpeg plate' and was shorted to ground. I repaired the wire and protected it with some spiral-wrap so it doesn't happen again.

Because of its reputation, it's easy to jump to the conclusion that the $ervo unit has gone south , when the real issue is elsewhere.

179411 said:

Finished up a alternator mod and clutch replacement on the ol' pig recently. After reassembling the bike and the brake system I proceeded to bleed said system using a vacuum bleeder on the four circuits as the battery was not yet installed. Imagine my horror upon testing the brake system with the battery in place and having no rear $ervo and experiencing the continuous 4Hz ABS light. Mercy! After another bleed hoping that I had screwed up the process I started to get... concerned... read that as excited.

While diagnosing the problem I removed the connector at the ABS unit so I could meter the footbrake microswitch (pins 7 and 41) to ensure that it operated. It did, or rather, it appeared to. I observed that the microswitch is normally closed when the footbrake lever is up, and opens the circuit when the footbrake lever is pressed to activate the rear brake servo. Hmmm.

Upon researching relevant information on the web I stumbled across this thread and after losing about three hour's sleep the next morning obsessing about the problem I wondered if the servo's active line could be grounded, just as the microswitch does, preventing the servo unit from initializing or activating the rear brake circuit. I metered both wires to ground and found that...

Sure enough, during reassembly of the bike, one of the two wires in the footbrake switch harness (the active wire, of course) had been pinched between the transmission and the RH 'footpeg plate' and was shorted to ground. I repaired the wire and protected it with some spiral-wrap so it doesn't happen again.

Because of its reputation, it's easy to jump to the conclusion that the $ervo unit has gone south , when the real issue is elsewhere.

Click to expand...

Slipping a bit off-topic here, I've been told that vacuum bleeding is NOT recommended for servo brakes due to the possibility of servo valve damage. It's not needed for the wheel circuits anyway, just turn on the key and let the servo pump the fluid when you squeeze the brake.

I was waiting for a few days to see if anyone would coroborate that information. I hadn't heard that using a vacuum bleed is not recommended with the whizzy brakes. I've done this twice now without difficulty, but I'm willing to change my procedure. GSAddict?

My Princess Auto bleeder doesn't pull much of a vacuum but seems to purge the circuits well enough. I was a bit concerned about the front brake lever feeling a tad soft, but under power it's operating normally with good feel and stoppage.

Tom

179411 said:

I was waiting for a few days to see if anyone would coroborate that information. I hadn't heard that using a vacuum bleed is not recommended with the whizzy brakes. I've done this twice now without difficulty, but I'm willing to change my procedure. GSAddict?

My Princess Auto bleeder doesn't pull much of a vacuum but seems to purge the circuits well enough. I was a bit concerned about the front brake lever feeling a tad soft, but under power it's operating normally with good feel and stoppage.

Tom

Click to expand...

I have always bled the control circuits F&R with my vacuum bleeder. Never had any issues.
The power side I do with a custom made graduated cylinder.
If you have a GS-911 there is a bleed test you can do on the integral brake system to ensure all the air is really out.