ABS Fault Lamp Fix

[R111S]

Disclaimer: Do not attempt to make this modification. I do not guarantee it will work for you. You are responsible for any modifications made to your motorcycle.

12MAY2007 – I’d been having ABS Fault Lamp problems on and off since the beginning of ownership. I found a good idea by Mick McKinnon on the Internet and decided to try it out with a minor change. I modified the ABS Wiring Harness to add a Momentary Off Switch into the Green Wire circuit that connects to Pin-15 of the 26 Pin ABS Connector. A test ride proves that it works well.

I use the Momentary Off Switch like this:

1) Start the engine and then note if the ABS Lamps are indicating a fault.
2) If so, press and hold the Momentary Off Switch a few seconds then let go.
3) The ABS Controller is reset and all is well...ride away as usual.

The Momentary Off Switch is mounted on the fairing panel just below the ABS Lamps.

[wswartzwel]

Am I missing something here? Why not repair whatever is causing the fault light to come on?

[R111S]

Originally posted by wswartzwel
Am I missing something here? Why not repair whatever is causing the fault light to come on?

Well said Bill but that would be more than I'd like to or even could do in this case. If I were fixing the ABS Controller I would include an input to it from the Electric Start Switch (is it On or Off position?). I'd then modify the Software so it would note that if the Starter Button is depressed then disable ABS Fault Tripping.

I'm working off the assumption that the ABS Controller, as spec'd by BMW, doesn't know when the Starter is cranking. I also assume the ABS Controller is tripping the ABS Fault because of the dip in battery voltage during cranking.

It makes sense to Fault the ABS and disable it if the Battery voltage is low, but in this case the Fault is prematurely tripped by low battery voltage during engine cranking. I don't know what the Low Voltage trip point is but I assume it's somewhere south of nominal.

This "Fix" basically resets the ABS Controller post engine cranking and thus nullifies the ABS Faulting on Low Battery Voltage during cranking.

[wswartzwel]

How old is the battery? Something must be amiss... they didn't kick fault codes when they left the dealer show room back in 99.

Should i bring my jumper cables for our ride in July to CO.???

[R111S]

Not sure about the age of the battery but it cranks fine...I think it's just old wiring that is becoming resistive over time.

[R111S]

So here it is ~34K Miles and almost 5 Years later (MAY2007) and the Momentary Off Switch I got from RadioShack has suffered a mechanical failure. The button has parted company with the switch body.

I bought a new replacement switch (same P/N: 275-1548, package of 4) from RadioShack for $3.99 (including tax).

Later that same year (AUG2007) I installed a Panasonic LC-X1220P VRLA Battery I'd bought from Electronic Components Distributor | DigiKey Corp. | US Home Page ($76.09 including shipping). This UPS Battery is still working well ~29K Miles and almost 5 years later. The Panasonic Data Sheet says "For main and standby power supplies. Expected trickle life: Approx. 6 years @25 Deg C, Approx. 10 years @20 Deg C".

I have a ProMariner ProSport 1.5 Trickle Charger that keeps this battery going when I'm not riding (Products :: Battery Chargers :: ProSport 1.5 Portable Maintainer).

Off the cuff, I'd say this ABS Reset Switch has been used nearly every day that I ride in the colder months and less so in Summer. This stands to reason since Lead Acid Batteries are negatively affected by colder ambient temperatures. All-in-all I'm really glad I made this mod.