wndsrfr
08-23-2005, 03:20 PM
Arrrrgggghh.............'92 K75RT ABS1 troubleshooting results so far:
1. ABS lites blinking continually.
2. Rear Modulator gets very hot to the touch--it gives no pedal---like air in the system, then locks up the rear wheel. Code #2 (Rear Modulator) shows on the LED. Fluid is bled thoroughly and bled again--it's solid as a rock with ABS disconnected.
3. Installed another rear modulator--same results.
4. Got a third rear modulator (Thanks Beemer Boneyard--Mike F.--you're a trooper!) and installed it....same results.
5. Second Brain ($380 used from individual claiming it to be good) seemed to make everything work until I applied the brakes several times on gravel road and the rear modulator went into mush/locking mode again. Now that brain gives code #7 (bad CPU) and won't reset from it. Brakes work fine in non-ABS mode.
6. Resistance test results following Brian Curry's IBMWR article show different values than he got. All three rear modulators and my front modulator show the same values with only one exception. However, there are different resistances shown by the DVOM if the leads are swapped, indicating that there's some diode circuitry in there that is shunting the power one way with test leads set up with black on the first (or lower numbered) test point versus the red lead being on the first test point.
ABS connector points 7,11,12
Test Vale------- Black on 1st / ----- Red on 1st /-----Per Brian's article
Resistance 7-11 -- 4.40K /------------ 4.35K / ------- 4.48K
Resistance 7-12 -- 6.53K (or 8.0K)* / -- 4.73K / ------- 16.7K
Resistance 11-12 -- 6.61K / ------------8.94K / -------- 19.5K
* Two of the modulators show 8K on 7-12, one shows 6.53K as does my front modulator (on points 6-10).
This is a big difference in resistance value versus those published by Brian--has anyone else found similar resistance values on your bikes?
Besides the pins 7,11 & 12 that connect to the ABS brain, there are two other pins on the modulator plug located at the 12 o'clock position (yellow wire to 87 on the ABS relay) and 3 o'clock position (brown-ground wire) --resistance on these is 6.85K with black lead on ground, 3.65K with red lead on ground.
Battery voltage is good--12.6v engine off, 13.6v running.
The ABS Relay checks 65 ohms on pins 17-19 and it functions fine when I cycle it with power directly on pins 85-86 and the contacts show zero resistance on pins 30-87 when it's cycled. Anyway, it's gotta be shooting plenty of power to the system in order to heat up that rear modulator that hot within 4-5 minutes of operation.
The fault code 7-bad brain checks for pins 1,3,17 are all open to ground as they should be.
I called the local dealer's shop & asked them if they could troubleshoot the brains--they said that their "Motronic" unit would diagnose the system on the bike and give a graphical output showing where the trouble is. Upon questioning, it seemed to me that their unit just taps into the pigtail and instead of showing blinking codes it displays something on a computer monitor doing the same thing that we do with the little LED light and the chart. Am I mistaken or can they actually probe the brain and the modulators?
OK, so what's all this mean? Do I have 4 bad modulators? Hard to believe that, somehow. Maybe it's two bad brains? Or three with mine thrown in? Has this fried your brain yet?
Anyone within 200 miles of Norfolk, VA who is willing to try my brains on your bike?--I'll ride over to you in a heartbeat....
John
1. ABS lites blinking continually.
2. Rear Modulator gets very hot to the touch--it gives no pedal---like air in the system, then locks up the rear wheel. Code #2 (Rear Modulator) shows on the LED. Fluid is bled thoroughly and bled again--it's solid as a rock with ABS disconnected.
3. Installed another rear modulator--same results.
4. Got a third rear modulator (Thanks Beemer Boneyard--Mike F.--you're a trooper!) and installed it....same results.
5. Second Brain ($380 used from individual claiming it to be good) seemed to make everything work until I applied the brakes several times on gravel road and the rear modulator went into mush/locking mode again. Now that brain gives code #7 (bad CPU) and won't reset from it. Brakes work fine in non-ABS mode.
6. Resistance test results following Brian Curry's IBMWR article show different values than he got. All three rear modulators and my front modulator show the same values with only one exception. However, there are different resistances shown by the DVOM if the leads are swapped, indicating that there's some diode circuitry in there that is shunting the power one way with test leads set up with black on the first (or lower numbered) test point versus the red lead being on the first test point.
ABS connector points 7,11,12
Test Vale------- Black on 1st / ----- Red on 1st /-----Per Brian's article
Resistance 7-11 -- 4.40K /------------ 4.35K / ------- 4.48K
Resistance 7-12 -- 6.53K (or 8.0K)* / -- 4.73K / ------- 16.7K
Resistance 11-12 -- 6.61K / ------------8.94K / -------- 19.5K
* Two of the modulators show 8K on 7-12, one shows 6.53K as does my front modulator (on points 6-10).
This is a big difference in resistance value versus those published by Brian--has anyone else found similar resistance values on your bikes?
Besides the pins 7,11 & 12 that connect to the ABS brain, there are two other pins on the modulator plug located at the 12 o'clock position (yellow wire to 87 on the ABS relay) and 3 o'clock position (brown-ground wire) --resistance on these is 6.85K with black lead on ground, 3.65K with red lead on ground.
Battery voltage is good--12.6v engine off, 13.6v running.
The ABS Relay checks 65 ohms on pins 17-19 and it functions fine when I cycle it with power directly on pins 85-86 and the contacts show zero resistance on pins 30-87 when it's cycled. Anyway, it's gotta be shooting plenty of power to the system in order to heat up that rear modulator that hot within 4-5 minutes of operation.
The fault code 7-bad brain checks for pins 1,3,17 are all open to ground as they should be.
I called the local dealer's shop & asked them if they could troubleshoot the brains--they said that their "Motronic" unit would diagnose the system on the bike and give a graphical output showing where the trouble is. Upon questioning, it seemed to me that their unit just taps into the pigtail and instead of showing blinking codes it displays something on a computer monitor doing the same thing that we do with the little LED light and the chart. Am I mistaken or can they actually probe the brain and the modulators?
OK, so what's all this mean? Do I have 4 bad modulators? Hard to believe that, somehow. Maybe it's two bad brains? Or three with mine thrown in? Has this fried your brain yet?
Anyone within 200 miles of Norfolk, VA who is willing to try my brains on your bike?--I'll ride over to you in a heartbeat....
John