Advice wanted regarding ST1100 TCS engaging randomly

[Henchman]

Hello all. I have an ST1100 ex police machine that I bought ten years ago and use sparingly.
On taking it out for its first spring run last week, the TCS has started cutting in, that is when driving normally the engine suddenly looses power and the TCS Light flashes on and off. The bike recovers quickly for a few miles then it happens again. I did not think the TCS actually worked until last week when it started playing up. The ABS has never worked, probably because the Nottingham Constabulary disabled it when the bike was being converted to police work.
My question is, where to start looking for the fault, or is there a simple way to disable the TCS? I tried pushing the TCS OFF button on the fairing first time this happened but that did not stop it cutting in a few miles further. All suggestions or guidance welcomed.
H

 

[Andrew Shadow]

I tried pushing the TCS OFF button on the fairing first time this happened but that did not stop it cutting in a few miles further.

Just as an F.Y.I. the motorcycle must be stationary to turn off the TCS if I remember correctly.

What condition is your battery and charging system in? I know that a weak battery or a failing charging system on an ST1100 will cause funny things to happen with the ABS system. I don't know if it affects the TCS the same way.

The TCS activating means that the computer thinks that the rear wheel is loosing traction. The TCS gets its input signal from the rear wheel ABS sensor. I would first have a good look at the rear wheel ABS sensor for anything abnormal. Sometimes it as simple as dirt build up on the sensor that screws everything up.

 

[jfheath]

My experience of this happening was when one of the sensors was about to fail. It would (sometimes) arm itself within the first couple of seconds when setting off, and then it would cut out. It did it for a couple of weeks and then the sensor failed.

But it could be the switch on your right knee. If I remember correctly, the Traction Control switch is a momentary contact switch. It doesn't stay on or off. It sends a pulse to the ABS control unit, which makes it change state - and I you can do that on the move. Maybe you have a dodgy wire or the switch contacts are dodgy. Something is making it turn off and then on again. Those are the only two things that I can image.

There's a trick I discovered to find out of the ABS unit is getting info from the sensors. I'll see if I can find it - unless it has got lost in the great post robbery. I'll be back.

https://www.st-owners.com/forums/threads/st1100-abs-fault-finding.158284/ May 13 2017. Thats when I posted it. I probably wrote it about 2006. It is in the section that I have labelled 'What the manuals don't tell you'. This was an ST1100AY so the ABS 2 system.

(All of the above is recalling events from 20 years ago. But I have a memory which is significantly less than that. But I wrote that at the time on my own website, then modified it for this site nmuch later. So what is on that page is everything that I found out about it at the time. If what I said in this post doesn't match what I have said in that article, then it will be the the article that is correct !)

Note the bit about how I 'solved' it. I broke off the sensor bracket. That really fixed it. But I did eventually get it working again - It cost me a new inner final drive plate, bearings and shims. And I found a 2nd hand sensor at the breakers yard.

 

[Henchman]

Thank you both for your useful input. My bike is an AX so your thread will definitely apply.
Is there a simple way to test the sensors, eg slowly spinning the wheel and watching the changes in the output voltage, or will I need to borrow an oscilloscope?
If necessary can I just unplug the sensors and forgo the TCS system, as the ABS has never worked and the braking on the ST is so much better than on my previous bike (CX500) ? The lack of ABS has never been pulled up on any previous MOTs.

 

[Erdoc48]

I have a 94 ABS1 bike and although it did work when I first got the bike in 2014, it hasn’t worked (well, I never truly activated it) in many years (meaning I never activated it on the road, but it would do its proper computer setup at start, then give me flashing lights on the ride). Anyway, I was getting all kinds of warning / flashing lights in the upper panel of the dash for ABS and the TCS light would stay on.

I’m a fair weather rider, so I didn’t remove any of the equipment, I just pulled all of the ABS fuses near the battery and got behind the dash panel and pulled the bulbs (but they’re still in the sockets) - just pulled them from where they can illuminate the dash lights. The issue is that I tried to pull codes a few years back and got some variability in the codes, plus, the parts are no longer available for the ABS 1 system (in the event it’s a sensor on the wheel). It brakes just fine, just not an ABS bike, and if I ever sell it, everything is still intact if the new owner feels they can or want to tackle the fault.

You’re in the UK, and I know Pans were police bikes there for many years- is yours newer so an ABS 2 version or the older ABS1?

 

[Firstpeke]

Now I would be guessing at potential faults here, but as someone has said, the ABS and TCS get their signals from the front and rear wheel sensors.

My initial thoughts were before you said it had been disabled by the Police workshop, which does make one think bad thoughts on a bike this big and heavy!

So then I thought that if the front sensor is intermittent that would cause the TCS to do likewise.

The sensors are both the same so if the gaps are correct between the sensor ring and the sensor then I would probably try swapping the actual sensors over physically and see what happens. When I say swap the sensors I mean completely, front to rear and the connections at the control module also!

If the fault is different then that would indicate that the front sensor, previously the rear now fitted to the front, would by implication be faulty.

If the fault remains the same it may be the ABS control module or whatever module does the ABS/TCS as my memory is bad given the 14 years since |I last owned an ST!

I can't remember if there is a fuse that supplies JUST the ABS/TCS but that would be the next thing to pull....

Perhaps do that last bit first, then decide your next move after that!

I would disconnect the on/off switch to eliminate a switch fault during testing.....

HTH

YEMV