ABS working or not

[RobertT]

hi all, I need some help/ advice. I have a 2006 ST1300 with ABS with 55000KM's. It seems that the ABS is not working however here is the interesting thing. When I start my ST the abs light is on as soon as I start moving the ABS light goes off, there is no flickering of the ABS light or other indication that the ABS is not working- according to the Haynes workshop manual from start to move the ABS is self diagnosing, I tend to use the brake before i start the ST- (in other words when I mount the ST i will engage the rear brake in order to keep the ST stationary and as soon as I turn the ignition on i can feel a pulse through the rear brake lever) and if the ABS light does go off the self check is successful. I have been suspecting that the ABS is non functional for a while, so a couple of weeks ago I saw a sandy patch on the tar and stomped on the rear brake and the rear wheel locked up- I even looked back to confirm the skid mark in the sand. Does any one know where to look or what the issue might be, I would prefer a "non-take apart approach".

 

[Igofar]

Throw away your Haynes manual and purchase a Honda service manual.
What your describing is the ABS working correctly.
When you start the bike the ABS light should come on, and remain on until the bike moves a few feet, it then turns off. This is what its supposed to do.
If the FI light or the ABS light flashes (blinks) continuously, or remains on while the bike is moving, then you have an issue.
I suspect your ABS is not at fault, but you could have some other issues with your brake system (research SMC-Secondary master cylinder) and have someone knowledgeable with these bikes inspect your SMC, Pads, Calipers, etc.
Sounds like your rear brake may be dragging due to a faulty SMC unit.
These systems need to be flushed out yearly to keep from seizing up and having issues.

 

[RobertT]

Hi Igofar.
Thanks for your reply. What you describe is exactly what happens. I did flush the whole brake system recently, replaced the piston on the SMC and bled the system through. I am aware of the rear wheel drag that occurs on the ST's. I did replace the rear brake pads about 2000km ago and the rear caliper is not binding. My concern is that the "self test" of the ST's ABS system is successful however there are no flashing lights from the FI or ABS-despite the OK from the motorcycle's electronic side the rear wheel is still able to lock-up. Is this not the point where that ABS should activate and prevent the rear wheel or front wheel from locking up? For a comparison I took a ride on a NC700 and when I tested the brakes there was a distinct continuous pulse on the brake pedal and lever whilst the ABS was engaged, does the ST1300 do the same or am i missing something?

 

[Igofar]

You said you REPLACED THE PISTON ON THE SMC? which means you tried to rebuild it?
That is probably most, if not all of your issues.
Replacing the piston in the bore, no matter how clean the bore looks, will not correct brake issues, or rear wheel lock up issues due to the SMC return port is not allowing pressure to return and bleed off etc.
there is a small screen cartridge on the back side of the SMC that will become clogged up and cause these issues.
This is why it is always better to replace the entire SMC as a whole unit, rather than try to rebuild it etc.
Flushing the brake fluid OUT will not do anything to correct the issue if the return port is clogged.
Go to the article section of this forum and find Mr. John Heaths write up on Avoiding the Pitfalls, this may help you understand your brake system better.
And yes, it is possible to lock up and slide your rear wheel due to these issues, even with ABS.
the down side is your brakes could also lock up without warning and pitch you off if you keep riding it before you sort out what the problem is.
Be careful.

 

[dduelin]

The ST’s ABS system and the NC’s ABS system behave the same in that they go through a self diagnosis test at engine start up. According to conventional wisdom and the Honda service manual if the dash ABS light goes off at 6 mph the system has self-tested and is working normally. If the system notes a defect while riding the system records and stores a problem code, switches on the ABS light, and switches off the ABS function. The brakes will work just not with ABS function and the light will blink until the defect is no longer detected. The code can be retrieved in order to identify the faulty part. When retrieving the code the pattern of blinking indicates the exact fault in the ABS system.

Thus if the rear wheel locked up a moment under rear brake pressure ABS could not have been operational and the system would begin to blink and the system would have recorded a code. If the light didn’t remain on after the event there was no defect detected. Operational ABS will brake a wheel just at the threshold of skidding and this can leave a “darky” or dark stripe on pavement. To explain the experience presented perhaps the wheel didn’t actually lock up?

A static test of the SMC is easy to do and absolutely should be done but I think it’s a red herring to the question of if the ABS is working normally.

 

[Igofar]

Dave’s right about the red herring, my OCD just got ahead of me and I started running causes in my head.
But you should still check your brake system out.

 

[RobertT]

thanks for the feedback, I will see if I can retrieve a fault code from the ABS over the weekend and revert back to you with my findings.

 

[jfheath]

Are your brake lights working when lever and pedal are operated ? I believe ( but don't know) that ABS will operate only when the brakes are applied and that may require the brake light switches to be working. An assumption made from looking at the circuit diagram. Someone please correct that if I am wrong.

The link mentioned by Larry is here

Article [13] - ST1300 Maintenance - Brakes- Avoiding the Pitfalls | ST1300 Articles

A close hands-on look at the Honda ST1300 braking system. These are personal observations about the things that can go wrong, why they go wrong and what can be done to keep things working sweetly. Updated April 2020 and to address more recent observations, to include information about the SMC...

www.st-owners.com

And info on the SMC...

Article [13] - ST1300 - Maintenance - Photos of dismantled SMC | ST1300 Articles

A faulty SMC, taken apart, sawn lengthways, with labelled photos and a commentary. This SMC had a brand new service kit fitted not long before it failed again. A while ago I posted a query concerning some weird behaviour on a friends braking system. The symptoms were that in spite of getting...

www.st-owners.com

and ...

SMC Info - 2008 Onwards | ST1300-Brakes

Some close up photos of a brand new SMC for 2008 models and later - including the measurement for the refitting of the plunger bracket. Above: In this photo, the rubber boot is pulled to one side to reveal the retaining circlip and washer. This is brand new, I am surprised that there is not...

www.st-owners.com

 

[dduelin]

thanks for the feedback, I will see if I can retrieve a fault code from the ABS over the weekend and revert back to you with my findings.

Well, if the light is not blinking at present (past 6 mph) there is no code stored. That is my understanding of the system.

If you don't have the procedure to retrieve the code I can make a copy and send it to you in a PM. Haynes may not cover it as well as the Honda service manual.

 

[Mellow]

Well, if the light is not blinking at present (past 6 mph) there is no code stored. That is my understanding of the system.

If you don't have the procedure to retrieve the code I can make a copy and send it to you in a PM. Haynes may not cover it as well as the Honda service manual.

Article [13] - ST1300 - FI Codes (MIL) Malfunction Indicator Lamp | ST1300 Articles

The PGM-FI MIL denotes the failure codes (the number of blinks from 0 thru 33). When the indicator lights for 1.3 seconds it is equivalent to 10 blinks. When more than one failure occurs, the MIL shows the blinks in order of lowest to highest number. Code Reset: Turn the engine stop switch...

www.st-owners.com

 

[dduelin]

Article [13] - ST1300 - FI Codes (MIL) Malfunction Indicator Lamp | ST1300 Articles

The PGM-FI MIL denotes the failure codes (the number of blinks from 0 thru 33). When the indicator lights for 1.3 seconds it is equivalent to 10 blinks. When more than one failure occurs, the MIL shows the blinks in order of lowest to highest number. Code Reset: Turn the engine stop switch...

www.st-owners.com

ABS defect codes are not stored in the PGM-FI computer and cannot be retrieved like FI codes. There is a separate process for ABS code retrieval and reset. I would have scanned and attached the service manual process to my post but I didn’t want to violate ©️.

 

[Mellow]

ABS defect codes are not stored in the PGM-FI computer and cannot be retrieved like FI codes. There is a separate process for ABS code retrieval and reset. I would have scanned and attached the service manual process to my post but I didn’t want to violate ©️.

Go for it, I doubt anyone really cares about a small scan.

 

[Ryan_B]

For what is worth, it is really impressive how much grip these bikes have. I had never activated my ABS during normal riding and decided I needed to just so I would know what it felt like if I were ever in a panic situation.

I checked it out on good asphalt, with no gravel and absolutely mashed the brakes at 15-20mph. It stopped so quick I either didn't activate or didn't notice the ABS. I tried a few more times with increasing speed and finally noticeably activated them after the 3rd or 4th try. Very non-intrusive in my opinion, I remember just slight pulsing on the handle. Nothing like an early 2000s car that sounded like a machine gun going off and vibrated your foot off the pedal. I don't recall if the ABS light ever actually turned on (of course I wasn't watching the dash).

@dduelin summed it up in the post above well. An ABS system just has magnetic pick up on each wheel that causes a pulse from the notched rings, that is why your ABS light goes off after a few mph as the ABS system "sees" wheel movement. If either wheel does not match speed during braking, it assumes a skid and applies ABS to the entire braking system to make sure that wheel is no longer skidding. On a vehicle with a failed system the ABS light will never go out since it never senses wheel movement to complete the self diagnostics.

When you have an intermittent sensor failure, you will basically have ABS every time you apply the brakes since it is not reading movement correctly, until eventually the system goes into failure mode and illuminates the ABS light and defaults to non-ABS braking. On traction control vehicles this intermittent fault becomes very dangerous as it also limits power when throttle is applied because it assumes wheel spin.

Going a little off course here, but the systems are of course ever-evolving. My 2015 Miata had the traction control system that could be turned off with 1 button push and allow wheel spin, however if it also sensed side motion g-force and if you did not have the throttle during a slide, it would instantly re-engage the traction system and control/stop the slide. You could defeat the entire system by holding the traction off button for 3-4 seconds, and it would cause a system fault, you would of course lose ABS, traction/stability control and run completely manual until you turned the car off and back on for a system start up.

All this to say, if the system has done its self check and thinks it is good, and you are still able to lock up the rear wheel, the only thing that could be wrong is the rear brake taillight switch is not working as @jfheath mentioned. The system needs to know you are applying brakes before it will activate. In theory the ABS pump could not be working too, but that would be an internal fault and should keep the ABS light illuminated.

Good luck! I just recently repaired a 2013 Chevrolet Express that had a intermittent wheel sensor problem. Turned out it was broken wire that would lose contact on bumps - but then re-connect immediately after. It basically was always randomly engaging either traction control or ABS while driving with no actual fault code stored/displayed.

Ryan

 

[dduelin]

For what is worth, it is really impressive how much grip these bikes have. I had never activated my ABS during normal riding and decided I needed to just so I would know what it felt like if I were ever in a panic situation.

I checked it out on good asphalt, with no gravel and absolutely mashed the brakes at 15-20mph. It stopped so quick I either didn't activate or didn't notice the ABS. I tried a few more times with increasing speed and finally noticeably activated them after the 3rd or 4th try. Very non-intrusive in my opinion, I remember just slight pulsing on the handle. Nothing like an early 2000s car that sounded like a machine gun going off and vibrated your foot off the pedal. I don't recall if the ABS light ever actually turned on (of course I wasn't watching the dash).

@dduelin summed it up in the post above well. An ABS system just has magnetic pick up on each wheel that causes a pulse from the notched rings, that is why your ABS light goes off after a few mph as the ABS system "sees" wheel movement. If either wheel does not match speed during braking, it assumes a skid and applies ABS to the entire braking system to make sure that wheel is no longer skidding. On a vehicle with a failed system the ABS light will never go out since it never senses wheel movement to complete the self diagnostics.

When you have an intermittent sensor failure, you will basically have ABS every time you apply the brakes since it is not reading movement correctly, until eventually the system goes into failure mode and illuminates the ABS light and defaults to non-ABS braking. On traction control vehicles this intermittent fault becomes very dangerous as it also limits power when throttle is applied because it assumes wheel spin.

Going a little off course here, but the systems are of course ever-evolving. My 2015 Miata had the traction control system that could be turned off with 1 button push and allow wheel spin, however if it also sensed side motion g-force and if you did not have the throttle during a slide, it would instantly re-engage the traction system and control/stop the slide. You could defeat the entire system by holding the traction off button for 3-4 seconds, and it would cause a system fault, you would of course lose ABS, traction/stability control and run completely manual until you turned the car off and back on for a system start up.

All this to say, if the system has done its self check and thinks it is good, and you are still able to lock up the rear wheel, the only thing that could be wrong is the rear brake taillight switch is not working as @jfheath mentioned. The system needs to know you are applying brakes before it will activate. In theory the ABS pump could not be working too, but that would be an internal fault and should keep the ABS light illuminated.



Ryan

There are a couple of misconceptions here about operation of the ST's ABS system. The diagnostic self check at start up involves more than just matching wheel speeds. Achieving wheel speed of 6 mph by both wheels sends a signal to the ABS control unit to begin the self-check. The ABS control unit cycles through the front and rear motor controls, the crank angle sensors F & R are compared to the ABS control unit to detect normal operation and the dash light goes out. If at any time while the motorcycle is in motion and the control unit senses a differential in wheel speeds beyond the programmed tolerance it runs the self-check again and if a fault is detected the system switches ABS off and the brakes revert to non-ABS operation. A code is stored and the light remains on until the code is reset and the fault repaired.

The rear brake light is not part of the ABS system and whether it works or not has no affect on ABS check and operation. If you can lock up the rear wheel and not have an ABS light go on and remain on the entire troubleshooting flow chart has to be run to detect the faulty component. There are 13 possible codes. The flow chart of system and component checks runs 25 pages in the Honda service manual.

 

[Ryan_B]

Thank you for the correction Dave! I know cars need the "brakes have been activated" signal to basically tell the ABS computer you are stopping, usually it is tied in to the brake pedal switch to the body control unit. Makes sense for this particular application it has to be a different since there is no BCU. Thank you for clarifying for this specific application and sorry to mislead anyone!

Ryan

 

[jfheath]

Yeah - my error - I thought I had seen the wire from the Brake light switch going to the ABS unit, once upon a time. I must have got cross-eyed looking at the diagram in the manual. There are two green and yellow wires running parallel to each other in the circuit diagram. One goes to the ABS unit - but it isn't the brake switch lead. Its an earth !