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jeffyjeff

ABS issue

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jeffyjeff

I have seen similar complaints posted to the BMWMOA forum, but so far, no reports of a cause or solution.  2002 R1150R ABS, 29,200 miles, pristine condition.

 

It happened without warning.  I was riding in the hills east of the San Francisco Bay and noticed my ABS light flashing.  The general fault (!) light was on steady and the ABS light flashing at 4 hz.  When I applied my brakes, it was apparent that my rear brake was in residual braking function (no servo assist).  I stopped at a pull out to investigate and poke around a bit, and when I started the bike, the problem vanished.  Over the next several days, I rode 160 miles without recurrence.  Earlier this week, I removed the tank and bled the brakes according to instructions (Flushing and Bleeding 101, Hager and Gilman; I believe originated at IllinoisBMWRiders.com). While I was at it, I also cleaned my ABS harness electrical connections using Stabilant 22, a contact cleaner and  conductivity enhancer.

 

All was fine, or so I thought, and then today, riding home from the post office, the ABS lights came on again (210 miles since the first occurrence).  I was accelerating from a traffic light when I noticed the lights.  I do not believe that a brake application initiated the fault.  Again, the rear brake reverted to residual function, and again, shutting off the engine and restarting cleared the symptoms.  This afternoon, I checked out the rear ABS sensor, air gap, and electrical connection.  I noticed the electrical connection (under the right rear cowl and just behind the evaporative system purge valve) did not appear to be latched fully.  The plastic connector latch was resting on top of the lock tab.  I cleaned the connection with Stabilant 22 and reassembled.  All seems well (again).  No recurrence during a 20 mile test ride.

 

My question:  Do you think that if the problem was indeed an intermittent open in the rear ABS sensor connection:  would the system resume normal function once the electrical connection made contact?  Is my system's reaction (flashing lights with residual brakes until key-off, key-on) normal for a momentary open in the sensor connector?  It is such an intermittent fault, it might be hard to nail down.  I hope that the unlatched connector was the cause.   Thanks for reading this and pondering my complaint.   Jeff  J.

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dirtrider
3 hours ago, jeffyjeff said:

I have seen similar complaints posted to the BMWMOA forum, but so far, no reports of a cause or solution.  2002 R1150R ABS, 29,200 miles, pristine condition.

 

It happened without warning.  I was riding in the hills east of the San Francisco Bay and noticed my ABS light flashing.  The general fault (!) light was on steady and the ABS light flashing at 4 hz.  When I applied my brakes, it was apparent that my rear brake was in residual braking function (no servo assist).  I stopped at a pull out to investigate and poke around a bit, and when I started the bike, the problem vanished.  Over the next several days, I rode 160 miles without recurrence.  Earlier this week, I removed the tank and bled the brakes according to instructions (Flushing and Bleeding 101, Hager and Gilman; I believe originated at IllinoisBMWRiders.com). While I was at it, I also cleaned my ABS harness electrical connections using Stabilant 22, a contact cleaner and  conductivity enhancer.

 

All was fine, or so I thought, and then today, riding home from the post office, the ABS lights came on again (210 miles since the first occurrence).  I was accelerating from a traffic light when I noticed the lights.  I do not believe that a brake application initiated the fault.  Again, the rear brake reverted to residual function, and again, shutting off the engine and restarting cleared the symptoms.  This afternoon, I checked out the rear ABS sensor, air gap, and electrical connection.  I noticed the electrical connection (under the right rear cowl and just behind the evaporative system purge valve) did not appear to be latched fully.  The plastic connector latch was resting on top of the lock tab.  I cleaned the connection with Stabilant 22 and reassembled.  All seems well (again).  No recurrence during a 20 mile test ride.

 

My question:  Do you think that if the problem was indeed an intermittent open in the rear ABS sensor connection:  would the system resume normal function once the electrical connection made contact?  Is my system's reaction (flashing lights with residual brakes until key-off, key-on) normal for a momentary open in the sensor connector?  It is such an intermittent fault, it might be hard to nail down.  I hope that the unlatched connector was the cause.   Thanks for reading this and pondering my complaint.   Jeff  J.

 

Morning  jeffyjeff

 

About all your (general fault  light  on steady and the ABS light flashing at 4 hz)   flashing dash lights tell is that one end of your brake system is in residual braking  (like you need flashing lights to tell you that).

 

An erratic or intermittent wheel sensor connection can make the ABS do strange things & light the warning lights  but usually only effects the ABS function not the power assist function. So in theory a bad wheel sensor signal shouldn't  effect the power braking part, just the ABS part. BUT, an intermittent wheel speed signal can change things. The return to normal after a restart could be pointing to a screwy speed sensor signal confusing the ABS controller (not real likely but possible)  

 

What you probably need to do is get a GS-911 (or dealer computer on that bike) as soon as possible after next rear power assist failure to get a real failure code (not just a dash warning light).

 

No way to know anything for sure from what you posted above but it sort of has the ear marks of an internal pressure sensor starting to fail. Or possibly a rear brake switch acting up (is rear brake switch adjusted properly with nothing caught in the switch area?) 

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jeffyjeff

Funny you should mention the rear brake switch.  About a month ago, the general fault light came on (without the ABS light) indicating an inoperative tail/brake light.  I checked the bulb, but it was still good.  related-unrelated???

 

I have a friend with a GS-911, and will contact him when he returns from vacation.  Any code logged in the system should still be there, right?  I suppose the ABS module stores codes in a non-volatile memory, but I haven't interrupted power to it, so any code should still be there.  When you say internal pressure sensor, does that mean internal inside the ABS module?

 

The brake switch is adjusted properly, with no obstructions in the microswitch, it appears to be working as designed.  I guess in the meantime I'll keep riding, knowing that root cause of the malady has not been corrected, and waiting for the next time the condition manifests.  Thanks for sharing your expertise.   Jeff J.

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dirtrider
18 minutes ago, jeffyjeff said:

Funny you should mention the rear brake switch.  About a month ago, the general fault light came on (without the ABS light) indicating an inoperative tail/brake light.  I checked the bulb, but it was still good.  related-unrelated???

 

I have a friend with a GS-911, and will contact him when he returns from vacation.  Any code logged in the system should still be there, right?  I suppose the ABS module stores codes in a non-volatile memory, but I haven't interrupted power to it, so any code should still be there.  When you say internal pressure sensor, does that mean internal inside the ABS module?

 

The brake switch is adjusted properly, with no obstructions in the microswitch, it appears to be working as designed.  I guess in the meantime I'll keep riding, knowing that root cause of the malady has not been corrected, and waiting for the next time the condition manifests.  Thanks for sharing your expertise.   Jeff J.

 

Afternoon jeffyjeff

 

About a month ago, the general fault light came on (without the ABS light) indicating an inoperative tail/brake light.  I checked the bulb, but it was still good.  related-unrelated???-- Bulb part is unrelated as that will only bring on the general warning light but rear brake switch could be a contributor.  

 

Any code logged in the system should still be there, right?-- Some are permeant  latching & others will self-clear  as soon as problem goes away, & others  will self clear after (x) number of ignition cycles. The best bet is grab the codes as soon as possible after the failure event.

 

When you say internal pressure sensor, does that mean internal inside the ABS module? -- Yes, a known problem area with the BMW I-ABS systems.

 

The brake switch is adjusted properly, with no obstructions in the microswitch, it appears to be working as designed..-- But is the micro switch actually working, making/breaking contact? The brake switches on the BMW I-ABS system are N/C & go open at brake apply (backwards to how most brake switches operate) 

 

The bad part of this whole deal is those internal pressure switches are a major failure point  on the BMW I-ABS (wizzy) braking systems. I think that Module Masters might now have those parts sourced so they can make the repair (you might give them a call with your symptoms as they are very friendly to talk with & can probably talk you through identifying the problem)

 

 

 

 

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jeffyjeff

Thanks for the clarification.  Yes, indeed; judging by the fact that I can hear the microswitch make and break contact, and also by the fact that the servo engages and the brake light illuminates when the switch is tripped, I would say that it is working as designed.  However, the wire from the switch to its connector was held in place by a zip tie that was tightened with Hulk-like strength.  Good to know that it is an NC switch, and conceivable to imagine an open in the wiring or connector could send a false signal to the ABS controller.  I'll get a GS-911 on it ASAP.   Then maybe I'll have more detail to share with Module Masters.   Have a great day!

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jeffyjeff

OK, yesterday we checked the codes with a GS-911.  The only code in the system was for the inoperative tail/brake light.

One thing stood out: the GS-911 reported system voltage at a measly 10.6 volts.  Voltage measured at the battery was on the order of 14 volts.  Somewhere, I have a pretty significant voltage drop going on.  I suspect harness grounds are a good place to start looking.  My Clymer manual wiring diagram shows the ABS control unit, Motronic controller, and diagnostic connector all terminate at a location called "gearbox ground".  Poking around with my flashlight has not revealed any ground point location.  Anybody know where "gearbox ground" is, and do you agree that finding and cleaning the grounds is an appropriate strategy?  I cannot imagine that a voltage disparity of such magnitude would be normal.   Some BMW owners point to bad batteries as a cause of servo-assist failure, and that gives me hope that maybe the pressure switches are not the root cause of my symptoms.

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dirtrider
10 minutes ago, jeffyjeff said:

OK, yesterday we checked the codes with a GS-911.  The only code in the system was for the inoperative tail/brake light.

One thing stood out: the GS-911 reported system voltage at a measly 10.6 volts.  Voltage measured at the battery was on the order of 14 volts.  Somewhere, I have a pretty significant voltage drop going on.  I suspect harness grounds are a good place to start looking.  My Clymer manual wiring diagram shows the ABS control unit, Motronic controller, and diagnostic connector all terminate at a location called "gearbox ground".  Poking around with my flashlight has not revealed any ground point location.  Anybody know where "gearbox ground" is, and do you agree that finding and cleaning the grounds is an appropriate strategy?  I cannot imagine that a voltage disparity of such magnitude would be normal.   Some BMW owners point to bad batteries as a cause of servo-assist failure, and that gives me hope that maybe the pressure switches are not the root cause of my symptoms.

 

Afternoon jeffyjeff

 

That does seem like low voltage but if the servo or servos were running at time of voltage trap then probably not to far out of line.

 

As a rule the BMW I-ABS system will report a low voltage code if the module thinks that the  voltage is low.

 

Clear the codes then see if you can grab another voltage reading with the engine running.

 

That   "gearbox ground" it a REAL pain to access so before going that route do a voltage drop test  between the ABS module ground & the battery (-) post. Do it with the servos running for max voltage drop to show up. 

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jeffyjeff

By ABS module ground, do you mean the brown wire that attaches to a screw terminal on the Motronic controller mounting bracket? 

BTW, all voltages reported above were with the engine running 3000 rpm in neutral,  no brakes were applied when the voltages were recorded.  Thanks,  Jeff J>

P7140432.JPG

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dirtrider
13 hours ago, jeffyjeff said:

By ABS module ground, do you mean the brown wire that attaches to a screw terminal on the Motronic controller mounting bracket? 

BTW, all voltages reported above were with the engine running 3000 rpm in neutral,  no brakes were applied when the voltages were recorded.  Thanks,  Jeff J>

 

 

Evening jeffyjeff

 

No, that is the Motronic RFI ground.

 

The ones to look at are the two brown wires going into the ABS module connector a .35mm & 2.5mm brown wire.

 

The smaller brown wire  should be the module electronics ground & the larger brown wire should be the servo motors ground.

 

You can run a basic resistance measurement but that only shows the no-load basic resistance. Doing a working (operating system) voltage drop test will show the resistance under load.  

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jeffyjeff

OK.  I got the cover off the ABS connector.  The 2.5mm brown wire is pretty obvious in pin #1.  But there are three candidates for the .35mm wire in pins #8, #27, and #28.  Any idea which one is the ABS module electrics ground?  I suppose I'll try to sneak a straight pin or sewing needle between the seal and the wire to make contact with the connector.  I can test continuity either with an ohmmeter to battery negative, or a voltmeter to battery positive (using a Craftsman digital multimeter) before attempting the voltage drop test.  

 

Your thoughts?

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dirtrider
15 minutes ago, jeffyjeff said:

OK.  I got the cover off the ABS connector.  The 2.5mm brown wire is pretty obvious in pin #1.  But there are three candidates for the .35mm wire in pins #8, #27, and #28.  Any idea which one is the ABS module electrics ground?  I suppose I'll try to sneak a straight pin or sewing needle between the seal and the wire to make contact with the connector.  I can test continuity either with an ohmmeter to battery negative, or a voltmeter to battery positive (using a Craftsman digital multimeter) before attempting the voltage drop test.  

 

Your thoughts?

 

Evening jeffyjeff

 

Pin 1 (large brown) & pin 28 (smaller brown wire).

 

For a resistance test you can just unplug the connector & use the exposed terminals in the connector  (that will also eliminate the module internals that could lower the resistance reading due to a low going back through the high (B+ side going  into the module)  that are attached to other external system loads). 

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jeffyjeff

I used a small paper clip to access the terminal behind the connector seal and then checked continuity to battery negative.  Once sure that the meter leads were making contact at both ends of the circuit, I switched the meter to Volts DC, turned on ignition power, and simultaneously applied front and rear brakes  (brake servo engaged).  Meter readings were recorded once the display stabilized (about 2 - 3 seconds of brake application).  A 1.5 Amp battery tender was connected to the battery during the test. 

 

ABS Terminal Pin #1 -     2.5 mm wire:  continuity = 000.0 ohms,   voltage drop 0.101volts

ABS Terminal Pin #28 -  .35 mm wire:  continuity = 000.0 ohms,   voltage drop 0.010 volts

 

I recall that when conducting a similar test on an automobile starter circuit, a drop of less than 0.5 volt would be considered acceptable.  But this is a much, much, much smaller circuit.  A 0.1 Volt drop seems reasonable for that size wire and the current flow it would be designed to carry.  No?.

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dirtrider
10 hours ago, jeffyjeff said:

I used a small paper clip to access the terminal behind the connector seal and then checked continuity to battery negative.  Once sure that the meter leads were making contact at both ends of the circuit, I switched the meter to Volts DC, turned on ignition power, and simultaneously applied front and rear brakes  (brake servo engaged).  Meter readings were recorded once the display stabilized (about 2 - 3 seconds of brake application).  A 1.5 Amp battery tender was connected to the battery during the test. 

 

ABS Terminal Pin #1 -     2.5 mm wire:  continuity = 000.0 ohms,   voltage drop 0.101volts

ABS Terminal Pin #28 -  .35 mm wire:  continuity = 000.0 ohms,   voltage drop 0.010 volts

 

I recall that when conducting a similar test on an automobile starter circuit, a drop of less than 0.5 volt would be considered acceptable.  But this is a much, much, much smaller circuit.  A 0.1 Volt drop seems reasonable for that size wire and the current flow it would be designed to carry.  No?.

 

Morning  jeffyjeff

 

With the circuit load of both servos running, the motor ground going back through the module terminal connection,  a connection to the transmission with a stud, then  back through the battery negative cable---  that 1/10 of a volt voltage drop really doesn't sound bad at all. Certainly not enough to cause  a latchable  low voltage ABS  condition on that circuit.  

 

There is/was a BMW service bulletin on the early BMW1150 bikes referring to low voltage conditions in the ABS  due to excessive brake usage then sitting still with brakes held on  (bulletin was mainly for the police  bikes used in training). It took a lot of brake usage with little or no recovery time between uses to lower the voltage enough to have the ABS system shut down though.

 

 But, the later fix (update) was applied to both the police bikes & the civilian 1150 bikes so apparently it wasn't a police-bike only issue . BMW went with a different (updated) electronics ABS module on the later 1150 bikes  that shut the rear power servo off at light rear brake pressure with bike sitting still. This updated ABS module  then  required a larger piston rear brake master cylinder to be used to have enough fluid capacity to allow proper rear braking under residual braking conditions.

 

Some of the 2002 1150 bikes were updated under BMW warranty if the ABS module failed & had to be replaced in service as the early ABS module was dropped from the parts system.

 

According to the old  BMW bulletin I have  the updated (revision 9)  ABS module went into production on the  R 1150 RT as of VIN ZE 87455.

 

The ABS module deal above is only to enlighten as a rider REALLY has to push the bike hard & use the brakes a LOT in a short time with  little or no  recovery between brake uses to get a low voltage ABS  malfunction.

 

You might clear all your ABS codes then see if anything returns in the future.

 

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jeffyjeff

Just checked.  The last 7 digits of my VIN are ZF46035.

 

Dirtrider, I'd like to thank you and express my sincere appreciation for all you have done to help riders like us to learn about and service our own motorcycles.  As we say in California, "You rock, dude".  (that is a compliment).

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dirtrider

Morning jeffyjeff

 

We still haven't cleared the entire system as you only verified the low (ground) side.

 

With that low system voltage showing  & engine running at 3,000 rpm's there might still be an issue on the supply side.

 

The ABS module gets it primary B+ from 2 inputs. The large diameter red wire that runs the servos & a smaller gray/black wire going into cavity #5 on the ABS connector (that gray/black wire B+ comes from fuse #2).

 

The large red wire gets it's B+ directly from the rear of the alternator.

 

So you might do a basic voltage check on those wires.

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jeffyjeff

OK, here we go.

ABS Connector Terminal #2,  Large (2.5mm) Red wire:  Voltage drop (front & rear brakes applied, servo engaged) Pin #2 > Alternator Output stud = 0.082 volts

ABS Connector Terminal #5, Small (0.35mm) Grey/Black wire: Voltage drop (both brakes applied, servo engaged) Pin #5 > Fuse #2 = 0.024 volts

I notice that it does not matter whether or not the brakes are applied on the small Grey/Black wire.  The voltage drop is 0.024 volts all the time.

 

Obviously, the engine was not running during any of these tests because the fuel tank was removed for access to the ABS controller.  But the aforementioned 1.5 A battery tender was connected and turned on.   Jeff J.

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jeffyjeff

So, if we add the total drops for the entire circuit:

The servo circuit shows  0.101 V + 0.082 V = 0.183 V

The ABS controller power circuit shows 0.010 V + 0.024 V + 0.034 V

 

Voltage drops appear reasonable (for a 17 year old system), eh?

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dirtrider
3 minutes ago, jeffyjeff said:

OK, here we go.

ABS Connector Terminal #2,  Large (2.5mm) Red wire:  Voltage drop (front & rear brakes applied, servo engaged) Pin #2 > Alternator Output stud = 0.082 volts

ABS Connector Terminal #5, Small (0.35mm) Grey/Black wire: Voltage drop (both brakes applied, servo engaged) Pin #5 > Fuse #2 = 0.024 volts

I notice that it does not matter whether or not the brakes are applied on the small Grey/Black wire.  The voltage drop is 0.024 volts all the time.

 

Obviously, the engine was not running during any of these tests because the fuel tank was removed for access to the ABS controller.  But the aforementioned 1.5 A battery tender was connected and turned on.   Jeff J.

 

Afternoon jeffyjeff

 

The large wire voltage drop doesn't seem excessive.

 

You might repeat the test but go to the battery (B+) post this time.

 

Also do a running-servo voltage measurement at the ABS module red wire (not voltage drop but actual voltage measurement) then compare that to same time period battery B+ post voltage measurement.  

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dirtrider
2 minutes ago, jeffyjeff said:

So, if we add the total drops for the entire circuit:

The servo circuit shows  0.101 V + 0.082 V = 0.183 V

The ABS controller power circuit shows 0.010 V + 0.024 V + 0.034 V

 

Voltage drops appear reasonable (for a 17 year old system), eh?

 

Afternoon jeffyjeff

 

Yes, voltage drops seem very reasonable-- the only this left verify is actual voltage available.

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jeffyjeff

Voltage available:

Grey/Black 0.35mm wire, terminal pin #5 to Bat negative:  key on = 11.75V   key on brakes applied = 11.46V

Red 2.5mm wire, terminal pin #2 to Bat negative:  key on = 12.22V     key on brakes applied = 11.80V

Bat + to Bat - measurement: 12.62V

 

Voltage drop:

Grey/Black 0.35mm wire, terminal pin #5 to Bat positive:  key on brakes applied = 0.448V (!)

Red 2.5mm wire, terminal pin #2 to Bat positive:  key on brakes applied = 0.109V

 

Instead of the 1.5A tender, I have a Craftsman 2A/10A charger available.  I could hook it to the battery at 10A charge, that would boost the Bat+ to Bat- voltage up to 14 volts or better (might do a better job of replicating actual charging system operation)  let me know.    Jeff J.

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dirtrider
1 hour ago, jeffyjeff said:

Voltage available:

Grey/Black 0.35mm wire, terminal pin #5 to Bat negative:  key on = 11.75V   key on brakes applied = 11.46V

Red 2.5mm wire, terminal pin #2 to Bat negative:  key on = 12.22V     key on brakes applied = 11.80V

Bat + to Bat - measurement: 12.62V

 

Voltage drop:

Grey/Black 0.35mm wire, terminal pin #5 to Bat positive:  key on brakes applied = 0.448V (!)

Red 2.5mm wire, terminal pin #2 to Bat positive:  key on brakes applied = 0.109V

 

Instead of the 1.5A tender, I have a Craftsman 2A/10A charger available.  I could hook it to the battery at 10A charge, that would boost the Bat+ to Bat- voltage up to 14 volts or better (might do a better job of replicating actual charging system operation)  let me know.    Jeff J.

 

Afternoon jeffyjeff

 

Grey/Black 0.35mm wire, terminal pin #5 to Bat positive:  key on brakes applied = 0.448V (!)-- That sort of points to losing something either through the ignition switch or through fuse #2. Might even be normal as at key-on a lot of 12v things go through the ignition switch & put a load on the key-on side of the system voltage.

 

Maybe try a voltage drop test across fuse #2 or at least measure voltage into & out of fuse #2. If the voltage in & out are both low then you are probably losing most at ignition switch, if losing some through the fuse #2 then replace the fuse.  

 

If you are losing a lot on  that Grey/Black 0.35mm wire, terminal pin #5 that could be part of your low voltage code  trap, Probably 1/2 volt drop isn't enough by itself but if the system is already low from engine idling (or key on & not even running, brake servos running, etc) then lights & accessories all on & working could lower your system voltage to start with, then put that 1/2 volt drop on top of that then maybe!     

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jeffyjeff

I checked fuse #2, and there is a 0.014V drop across the fuse - insignificant.

For grins, I hooked up my 10A charger to the battery and repeated the voltage drop to Bat+ and applied voltage to pin #5.  The results exactly duplicated what I had with the tender.  11.75 V at pin #5 seems reasonable to me (at least not worth doing exploratory surgery on the wiring harness).   I am satisfied in the knowledge I've gained here, and even though we did not find a definitive cause, I am satisfied that I've done all I can, short of replacing the ignition switch and ripping the harness apart.  (I've done that before, on a Honda Pacific Coast that had serious ground circuit issues, but right now, I am loathe to go there).  Yes, a 0.448V drop is concerning, but so is the possibility of causing unintended consequences in trying to find the source of the voltage drop.  I am about to button everything up, install the fuel tank, and clear the code.

 

I think I'll look further into my rear brake switch.  The fact that it is a NC switch coupled with the small wire gauge and the gorilla tight zip tie I found - point to a possibility (however remote) that a momentary open could send a brake signal to the ABS controller without corresponding hydraulic pressure from the rear brake master cylinder.  Thanks again for sharing your valuable expertise.   Jeff  J.

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dirtrider
1 hour ago, jeffyjeff said:

I checked fuse #2, and there is a 0.014V drop across the fuse - insignificant.

For grins, I hooked up my 10A charger to the battery and repeated the voltage drop to Bat+ and applied voltage to pin #5.  The results exactly duplicated what I had with the tender.  11.75 V at pin #5 seems reasonable to me (at least not worth doing exploratory surgery on the wiring harness).   I am satisfied in the knowledge I've gained here, and even though we did not find a definitive cause, I am satisfied that I've done all I can, short of replacing the ignition switch and ripping the harness apart.  (I've done that before, on a Honda Pacific Coast that had serious ground circuit issues, but right now, I am loathe to go there).  Yes, a 0.448V drop is concerning, but so is the possibility of causing unintended consequences in trying to find the source of the voltage drop.  I am about to button everything up, install the fuel tank, and clear the code.

 

I think I'll look further into my rear brake switch.  The fact that it is a NC switch coupled with the small wire gauge and the gorilla tight zip tie I found - point to a possibility (however remote) that a momentary open could send a brake signal to the ABS controller without corresponding hydraulic pressure from the rear brake master cylinder.  Thanks again for sharing your valuable expertise.   Jeff  J.

 

Afternoon jeffyjeff

 

That sounds reasonable.

 

If your problem returns & you think it could be a low voltage issue then you could do a very easy micro relay install using the present Grey/Black wire from ign switch to trigger the relay then grab a fused 12v source to power the relay. That way the #2 fuse & ign switch would be bypassed to power the #5 terminal.

 

With a little creativity you could do most of it right at the #2 fuse in the fuse box  as you have the  ignition switch (in) on one side of the fuse  (to trigger relay) & the other side of the fuse is a fairly low resistance  circuit between the fuse (out) & pin #5 at the ABS module.  So it could always be done later without removing the fuel tank or plastics.  

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jeffyjeff

I like the way you think!   Thanks!

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