ABS - error 8 - power circuir

Joined
Oct 21, 2016
Messages
43
Location
Rome (Italy)
Bike
ST 1100 ABS-TCS 1993
In the last three days the abs light flashes in the morning, on the way to work, 10/15 min after the start, when I'm waiting at the traffic light. If I turn off and restart the bike, the system operates regularely for all the day. The error code is nr. 8 (power circuit fault). The only thing I noticed is that the modulator (perhaps the rear one) noise is a little bit longer than usual. Any suggestion more than checking all the electrical connections ?
 

wjbertrand

Ventura Highway
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Feb 8, 2005
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What year ST1100? For the early models with the 28A stator (as opposed to the 40A alternator fitted to '96 and later) they charge poorly at low in-town and heavy traffic speeds. Eventually the battery gets drawn down to the point where the ABS doesn't have enough juice to function so signs off. Make sure to turn off any accessories at low speeds, especially high draw things like heated gear or auxiliary lighting.

Besides checking the battery terminals as suggested by Uncle Phil, check the starter relay and alternator 3P connectors for signs of overheating and burning whilst you have the left side cover off.

This could also be a sign that your battery is about to go kaput or worse the stator itself.
 
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roby_59
Joined
Oct 21, 2016
Messages
43
Location
Rome (Italy)
Bike
ST 1100 ABS-TCS 1993
First check: yesterday I've checked and cleaned the battery connections (not so bad) and all the ABS connectors behind the lateral fairing panels. All the connectors looked fine out of the one of the rear weel sensor, in this connector the wires insulators were deeply cracked (only on one side of the connector, all the other cables are perfect !). I've taped them. I'l keep you informed about the result.

bye, Roberto
 
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roby_59
Joined
Oct 21, 2016
Messages
43
Location
Rome (Italy)
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ST 1100 ABS-TCS 1993
When I had a sensor fault in my 2000 ABS/TCS ST1100, I discovered something that may help. I found this out by accident one day and I wrote it down and then repeated the process when I got my replacement sensor to see if it really did work. It seemed to.

The ECU will record a fault if the sensors stop working during the course of riding.
ie - they have been working, but then they stop working - so a fault is recorded. However, if it is a faulty sensor, the system will never store the same code again.

Note that the same error code is stored if after arming itself, the system detects that one wheel is rotating faster than the other (eg wheelies, very bumpy ground, putting bike on centrestand)​

The ECU will NOT record a fault if the system fails to arm itself when you start out.
My experience is that the ABS and TCS warning lights come on and stay on when one sensor isn't working. Because the system hasn't armed itself by verifying that both wheels are turning at the same speed, it cannot check if the sensors are working or not. One faulty sensor, or problems with the connectors / wiring loom will cause this to happen, and there will be no recent fault code stored in the ECU. Only historic ones will show up. So - if you get a faulty sensor, you will never see the sensor error code again after the code has been cleared from memory, or after other (possibly false) errors have over-written the stored errors.​

So - without an error code, how do you check if a sensor is faulty ?
Before doing this, make sure that you have recorded the 1 or 2 codes that have been stored - because you are about to clear them from memory !


Try to retrieve the problem code as before (yes I know you've done it already. Do it again).

• Clear the problem code (yes - even if there wasn't a fault recorded)
• Do NOT turn the ignition off.

At this point the lights look just like they are when you turn the ignition on - but this is not the case. Only if you have gone through the above procedure can the following test be carried out.

• Spin the wheel as fast as you can and watch the ABS warning light. If it flashes, the sensor is working. (nb - you will need a mirror or a friend to check this for the front wheel - the light only flashes while the wheel is in motion. The back wheel is easy, you can start the engine and slip it into gear)


And of course, a useful check is that the two sensors are interchangeable - front/rear.
They are a bit difficult to remove, and I would suggest pulling a bit of string through when you remove the sensors to make it easier to thread the cable afterward. The front sensor cable clip requires a knack to get it unclipped. I don't have that knack. It came apart after much prodding and fumbling.​
Luckily It’s a couple of days that everything’s going right, anyway the fault (code 8) always occurred after the rotation check and never while running. I hope it could be an electric problem due to the poor insulation of the sensor cables (that I’ve fixed). Anyway thank you for the explanation, I hope it can be useful to other members. Now I’m realizing that, sometimes ago, another fault occurred after a bump, but I haven’t the code because I’ve cleaned it by mistake.
 

wjbertrand

Ventura Highway
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I don't think a sensor cable problem would cause a code 8, more likely that would cause a code for the affected sensor.
 
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roby_59
Joined
Oct 21, 2016
Messages
43
Location
Rome (Italy)
Bike
ST 1100 ABS-TCS 1993
I don't think a sensor cable problem would cause a code 8, more likely that would cause a code for the affected sensor.
I agree with you, I don’t know if the sensor is electrically powered or passive, and if the ABS control unit can detect low voltage or short circuit, anyway now the system works. Maybe the cleaned battery contacts……
 
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roby_59
Joined
Oct 21, 2016
Messages
43
Location
Rome (Italy)
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ST 1100 ABS-TCS 1993
It happened again !!

I stopped at the traffic light with the rear brake pressed, the rear modulator vibrated and the light started flashing. I turned off/on the key, normal abs check and no flash. Normal operation untill I've reached the office. This time I've noticed two fault codes: the first is nothing (only long flash) and the second is 8.

Now my question is: is it normal that the modulator operates when the bike is not moving ? Any contribution will be appreciated.
 

wjbertrand

Ventura Highway
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The modulators perform a self test periodically. If there's a fault found the ABS light will be illuminated. The rear brake lights pull system voltage down a surprising amount and that 28A stator doesn't supply much juice at idle speed. Find a way to monitor your system voltage when riding, I'll bet it's dropping below the ABS sign off threshold.


Sent from my iPhone using Tapatalk
 
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roby_59
Joined
Oct 21, 2016
Messages
43
Location
Rome (Italy)
Bike
ST 1100 ABS-TCS 1993
The modulators perform a self test periodically. If there's a fault found the ABS light will be illuminated. The rear brake lights pull system voltage down a surprising amount and that 28A stator doesn't supply much juice at idle speed. Find a way to monitor your system voltage when riding, I'll bet it's dropping below the ABS sign off threshold.
next step:

1) idle rising
2) Voltmeter

Question: led stop light could help ?
 

wjbertrand

Ventura Highway
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Idle should be around 1,100 RPM but the 28A stator doesn't really put out its max until around 5,000 RPM. When I upgraded to the 40A alternator, this was the biggest difference, I had full system voltage from idle, even in slow traffic with the brakes and cooling fans cycling - lots more area under the curve. I think Honda made a mistake to equip the early ST1100s with a stator that was originally designed for models with higher RPM engines.
 
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roby_59
Joined
Oct 21, 2016
Messages
43
Location
Rome (Italy)
Bike
ST 1100 ABS-TCS 1993
Idle should be around 1,100 RPM but the 28A stator doesn't really put out its max until around 5,000 RPM. When I upgraded to the 40A alternator, this was the biggest difference, I had full system voltage from idle, even in slow traffic with the brakes and cooling fans cycling .....
Hoping not to be forced to upgrade the alternator, is there anything else I can do/check/upgrade in the wiring that could help ?
 

wjbertrand

Ventura Highway
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Hoping not to be forced to upgrade the alternator, is there anything else I can do/check/upgrade in the wiring that could help ?
The only thing you can do is to ensure all of the connections are tight and clean and permanently fit a voltmeter and carefully manage your accessories when in town/traffic. Keeping the battery in really good shape helps too. Even if you throw an occasional code 8 it's easy enough to cancel it out once you know the cause.
 
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roby_59
Joined
Oct 21, 2016
Messages
43
Location
Rome (Italy)
Bike
ST 1100 ABS-TCS 1993
The only thing you can do is to ensure all of the connections are tight and clean and permanently fit a voltmeter and carefully manage your accessories when in town/traffic. Keeping the battery in really good shape helps too. Even if you throw an occasional code 8 it's easy enough to cancel it out once you know the cause.
Voltmeter check:
1) Switch/off: 12.3 V
2) Idle (cold bike - 1000 rpm) low beams off: 12.1 V
3) Idle (cold bike - 1000 rpm) two lamps - low beams on (in Italy are required by law): 11.8 V
4) Idle (cold bike - 1000 rpm) low beams + stop light on 11.0 V ___Problem Found !!
5) 2500 rpm low beams on: 13.0 V.

It's time to install a voltmeter........
 
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wjbertrand

Ventura Highway
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Feb 8, 2005
Messages
4,407
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Ventura, CA
Keep in mind that system voltage will drop a couple of tenths further when everything is warmed up. Wires exhibit more resistance to current flow as they become warmer. My ST1300 will show 14.3 V when first started from cold and then settle to 14.1 V after few miles when it's fully warmed up.
 
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