2003 K1200GT Brake Failure light illuminated/No Brake/Tail light

[obtusegoose]

I have an electrical question for the resident motorcycle experts that doesn’t seem to have been answered previously in the forum as evidenced by searching for the problem.

The motorcycle in question is a 2003 K1200GT (ABS III/Integral brakes (“whizzy”) with 67,000 miles on it and has always run great with minimal problems. It has some additional running lights on it and a loud horn that I installed awhile back. The only major issue encountered was the dreaded clutch o-ring failure which was fixed 2 years ago.

I have performed all regular maintenance (oil/filter changes, spark plug renewal, coolant change, brake fluid bleeding (including ABS unit), accessory lights installation, etc.) so I am fairly accomplished mechanically.

I recently performed the two-year brake fluid change (including the fluid in the ABS unit which necessitates battery removal) and all appeared to go fine. (I’ve performed this service at least 4-5 times in the past and never have had issues doing it.) Prior to battery removal for the ABS flushing, when turning the vehicle on, it went through the “ABS check” noises and appeared normal. The battery was removed and the ABS unit flushed. When re-installing the battery, the battery holder bracket briefly touched the positive terminal and grounded on the bike frame emitting a spark. (I know, rookie mistake having battery negative connected prior to installing battery hold down.) All appeared fine so key was turned on but ABS check noises (whizzy sound test) don’t occur and brake failure light on dash stays illuminated. It was noticed that tail light and brake light won’t illuminate (installed additional lights tied into rear lighting wires won’t illuminate either) even though all other features work (license plate light, high/low beam, horn, windshield motor, blinkers, etc.). Motorcycle also starts right up and appears to run fine on the center stand (didn’t go for actual ride due to the tupperware being removed).

Here’s what I’ve checked so far:

• all brake fluid reservoirs ¾ full or more
• both front and rear brake light switches were activating prior to battery removal and bike was performing ABS self-check (whizzy sound) and all appeared normal
• battery is ½ year old and at 12.78 V (turns starter very energetically when bike is started)
• rear bulb (two filament) was checked (continuity) and is good
• tail light socket cleaned (looked good)
• rear brake pedal switch checked fine (continuity ceases when pedal is depressed)
• wires feeding tail light checked for continuity (from connector under right side seat) - checked good
• putting key in “parking position” illuminates tail light and front parking bulb (and accessory lights tied into tail light wiring)
• (above indicates tail light/brake light socket and wiring as being good)
• ABS relay in electronics box checked and operates fine
• all fuses under seat checked for continuity and check out fine
• electronics box under gas tank was inspected and all looked normal
• all wiring throughout bike checked for overheating, etc. and none found
• multi-wire connector for ABS unit pulled back to inspect wiring connection and all appears good
• all other functions on the bike operate as they should except brake light/tail light, flashing ABS light and start up whizzy ABS brakes sound/test

Questions:

• So has my ABS unit been potentially fried due to the brief battery short?
• Is there another fuse/relay to check somewhere on the bike (in the ABS unit?) for the ABS unit to initiate its start up check sequence and provide the rear brake light and whizzy brakes?
• Would a diagnostics reset (Hex GS911 unit, dealer diagnostics visit) clear ABS faults and render the ABS functional again so I get the servo assisted brakes?
• Other checks I should make to rule out a dead ABS unit?

Help me get the bike back on the road! Thanks.

 

[AntonLargiader]

So has my ABS unit been potentially fried due to the brief battery short?

Potentially, yes. I once touched the wrench to the ABS unit when removing the battery lead on a boxer. It blew one of the power MOSFETs on the ABS circuit board (GS Addict repaired it for me). If you actually touched the ABS unit then you duplicated what I did. If you touched something that is connected to it, same thing. The ABS unit itself is not heavily grounded so current reaching it looks for a path to go somewhere which it seems to do via the circuitry.

 

[obtusegoose]

Potentially, yes. I once touched the wrench to the ABS unit when removing the battery lead on a boxer. It blew one of the power MOSFETs on the ABS circuit board (GS Addict repaired it for me). If you actually touched the ABS unit then you duplicated what I did. If you touched something that is connected to it, same thing. The ABS unit itself is not heavily grounded so current reaching it looks for a path to go somewhere which it seems to do via the circuitry.

Thanks for the response. I recognize your name in the forum and appreciate your knowledge toward the K series bikes.

I'm pretty sure I grounded to the frame for a brief second and not the FTE ABS unit but understand your response in how the ABS unit could have been fried.

I did try going for a short ride with the tupperware off to see if it would correct the ABS fault - it did not.

I haven't checked the front brake switch/connector to rule that out. Is it located under the seat near the rear brake connector and low brake fluid connector?

Any thoughts if it is worth it to purchase the GS911 diagnostic unit to clear faults/cycle the ABS unit in hopes to resurrect it? (It is a bit pricey but a dealer visit would be at least that.)

Have you removed the ABS unit on a bike and directly connected the brakes from the master cylinder to the caliper? Are the braking results good enough to continue ownership of the bike?

I may get into the PCB in the ABS unit to check for damage. Any idea what MOSFET was changed or other info on it?

Thanks for your help.

 

[GTRider]

If it were my bike… before opening the ABS electronics I’d try borrowing a known good turn signal relay and see what happens with that in place. The reason I say that is the 03-04 GT use the same relay as the R1150RS, and I once spent a LOT of time chasing a non-functioning ABS unit and weirdness with lights on an 1150RS, to the point of being convinced the ABS unit was fried, only to discover the problem was a failed aftermarket turn signal relay. When that was replaced with a good BMW relay the ABS functioned normally and the light problems disappeared. That sounds like an odd approach to a brake problem, but BMW has A LOT going on in that relay, which is probably why it’s such a $pendy item.

FWIW,

DeVern

 

[AntonLargiader]

I haven't checked the front brake switch/connector to rule that out. Is it located under the seat near the rear brake connector and low brake fluid connector?

It's probably up in the front fairing.

Any thoughts if it is worth it to purchase the GS911 diagnostic unit to clear faults/cycle the ABS unit in hopes to resurrect it? (It is a bit pricey but a dealer visit would be at least that.)

There's no need to clear codes. When you fix the problem, the lights will go out and the brakes will work again

Have you removed the ABS unit on a bike and directly connected the brakes from the master cylinder to the caliper? Are the braking results good enough to continue ownership of the bike?

I've done that once or twice. Brakes are still pretty good.

I may get into the PCB in the ABS unit to check for damage. Any idea what MOSFET was changed or other info on it?

I blew a few traces that were visible to the eye and I repaired, but it still didn't work. The pumps did work when I energized them directly. There are two big power MOSFETs on that board, one for each pump. I don't know the spec because someone else repaired that part.

 

[AntonLargiader]

Something else... on that model there are two negative cables. When you remove the battery it's really easy to lose one of them under the tank and not realize it. Make sure both are attached.

 

[obtusegoose]

Just wanted to give an update and close out this thread.



After consulting with Tyler at Module Master, I removed the ABS ECU from the ABS module on the bike and sent it to them. After in their possession for approximately 2 weeks, it was returned with a few noticeable fixes to the PCB. It was re-installed in the bike’s ABS module and now it performs the pre-test and all other problems are gone and it performs flawlessly.



Thanks to all who responded.



Lesson learned - don’t accidently short the bike’s battery terminals when re-installing.

 

[motormike]

Just wanted to give an update and close out this thread.



After consulting with Tyler at Module Master, I removed the ABS ECU from the ABS module on the bike and sent it to them. After in their possession for approximately 2 weeks, it was returned with a few noticeable fixes to the PCB. It was re-installed in the bike’s ABS module and now it performs the pre-test and all other problems are gone and it performs flawlessly.



Thanks to all who responded.



Lesson learned - don’t accidently short the bike’s battery terminals when re-installing.

I know this is an older post but had to ask: I thought Module Masters (Idaho) was never able to come up with a parts suppler to fix the servo-ABS used on the 2003 and up K bikes? If you go to their web site it says "Not Available" and the following:

This rebuild is currently WAITLISTED and the waitlist is closed due to overwhelming demand.​

 

[pauls1150]

As I understand it, and I could be off-base here, they don't have a stock of parts for the hydraulic repairs.
If the issue is in the PCB, they may troubleshoot and repair that.
From their F.A.Q. page - We are currently unable to test Engine Control Modules. We can test some specific circuits and various components of the circuit board, but we are unable to test the entire module.