ABS problem

[coxy]

Looking for some advice on the ABS/modulator unit on a 2004 GS. It's remaining switched on after I turn on the ignition. I have already completely bled the brakes, both front and back. Both microswitches on the front and back brake lever and pedal seem to be fine, operating as they should. My GS911 unit tells me there is an error "24954: Internal control module error - Analogue value, front pressure sensor".
So I have two questions;
(1) I'm assuming the pressure sensor inside the modulator is stuck on, (if it has a mechanical component) so I intend stripping it down and cleaning it out to see can I free up the sensor. Has anyone done this before, and is the sensor constructed in a way that it can actually be stuck in the 'on' position, and freed by cleaning it/freeing it up?
(2) Also, I'm a bit confused with the front microswitch. When I pull the handlebar brake lever I can hear the switch click on and the rear brake light comes on as normal. The confusing thing is when I disconnect the microswitch by pulling out the wiring connector, this cuts out the modulator. That doesn't make sense to me as the microswitch is already open, (that is, until the break lever is pulled and closes the switch). I have already dismantled this switch and put it back together to make sure it's ok inside, and it is. (The lever is not in contact with the hand guard by the way).
The tone of the modulator changes when both front and back brakes are applied, which suggests the modulator is actually working. It's just why it is constantly switched on is the issue I need to solve.
Any advice welcome before I pull the modulator out of the bike on Saturday
Thanks

 

[Pukmeister]

Front brake keeps servo pump running continuously, rear brake lets it build pressure and cut out. I'd suspect fault is related to front brake switch signal.

If it's still running after turning off ignition, I'd suspect headstock wiring or ignition switch contacts at fault keeping ABS servo pump live when it should be turning off via CANBUS.

 

[coxy]

Front brake keeps servo pump running continuously, rear brake lets it build pressure and cut out. I'd suspect fault is related to front brake switch signal.

If it's still running after turning off ignition, I'd suspect headstock wiring or ignition switch contacts at fault keeping ABS servo pump live when it should be turning off via CANBUS.

Thanks for the reply Adam.
Can I ask you to give me a little more info? When you say the "rear brake lets it build pressure and cut out" can you explain this process a bit more so I can understand the mechanics of the system.

Also, It's doesn't usually keep running after I turn off the ignition, but this has actually happened two or three times when I was bleeding the system. I have checked the wiring loom and don't see any damage, I'll take another look to be sure. Ill also have a look at the ignition, anything I need to bear in mind when disassembling it, I.e. does it cause any problems with the computer when put back together again?

Thanks again.

 

[Pukmeister]

On my previous 2004 bike with ServoABS, operating the front brake lever at standstill kept the servo pump running continuously resulting in a dimmed headlight and drain on the battery/alternator.

Holding the bike on the rear foot brake instead, the pump would run briefly to build pressure then cut out. Every now and then the pump would briefly cut in and boost the rear brake pressure again which could be felt as a sharp pulse through the brake pedal.

For holding the bike on an incline I learnt to only use the rear brake to prevent a drain on the battery via the ServoABS unit.

Now you've mentioned that it keeps running since you've bled it, did you bleed and refill the internal reservoirs in the ServoABS until under the fuel tank, or just the plastic handlebar/rear pedal reservoirs?

The ServoABS unit has it's own pipe work system to the slave cylinders, the piping from the master cylinders to ABS unit is just a pilot system which also acts as a secondary (weaker) system in the event of Servo failure (aka residual braking).

The GS911 error code you mention can be caused by the internal fluid reservoirs in the ServoABS pump being too low, usually because wear in the front brake pads has caused the level to drop. Check your front pad thickness. Steptoe sells Ferodo pads at a good price (or sell a kidney and buy from a main dealer).

 

[The Grey One]

You did bled all the system and not just the front and rear calipers?

John

 

[coxy]

On my previous 2004 bike with ServoABS, operating the front brake lever at standstill kept the servo pump running continuously resulting in a dimmed headlight and drain on the battery/alternator.

Holding the bike on the rear foot brake instead, the pump would run briefly to build pressure then cut out. Every now and then the pump would briefly cut in and boost the rear brake pressure again which could be felt as a sharp pulse through the brake pedal.

For holding the bike on an incline I learnt to only use the rear brake to prevent a drain on the battery via the ServoABS unit.

Now you've mentioned that it keeps running since you've bled it, did you bleed and refill the internal reservoirs in the ServoABS until under the fuel tank, or just the plastic handlebar/rear pedal reservoirs?

The ServoABS unit has it's own pipe work system to the slave cylinders, the piping from the master cylinders to ABS unit is just a pilot system which also acts as a secondary (weaker) system in the event of Servo failure (aka residual braking).

The GS911 error code you mention can be caused by the internal fluid reservoirs in the ServoABS pump being too low, usually because wear in the front brake pads has caused the level to drop. Check your front pad thickness. Steptoe sells Ferodo pads at a good price (or sell a kidney and buy from a main dealer).

Thanks Adam, I know what you mean now, I have experienced the rear brake doing that alright.

John, yes, I have bled all 4 parts of the ABS system.

When this problem started I changed all brake pads, front ones weren't too bad but the rear ones had just gone past the grooves so needed to be changed. I had hoped this was causing a low brake fluid level in the Modulator but it didn't seem to be the problem.
Didn't get time to do anything today but will have a look at the ignition in the morning. I really don't want to take the unit off the bike unless its the last resort.
Thanks for the replies, will let you know how I get on tomorrow

 

[paddy dougan]

Had the same problem,
Only permanent cure, rip the useless piece of shit off, best thing I have ever done!! Brakes are much better feel wise and I decide when the rear comes on not the feckin bike. But that's my preference, very easy to do on your model year, just use the electric side of the modulator (dissconected from hydraulics first) for your speedo to work.
Pads

 

[Pukmeister]

Coxy, if all else fails it might be worth speaking to Steptoe. He has some insider knowledge about these Servo units that he keeps to himself for obvious reasons being an independent GS specialist, but he might be best able to advise you on repairs based on his knowledge/experience.

 

[oldchris]

I've told you once it's in two minds, just give it a good dose of talking to. Also, on a professional level a note of caution, you are becoming emotionally involved.

Sent from my GT-I9300 using Tapatalk

 

[coxy]

Thanks Paddy, that is an option if all else fails but I don't want this f¥¥kin thing to beat me. The unit is actually working, I just need to find out why it's on all the time.

Pukmeister, I'll give Steptoe a shout when I get a chance to check the wiring around the headstock and ignition, thanks.

And Chris, I'll take your advice, I should have listened to you before

 

[paddy dougan]

Thanks Paddy, that is an option if all else fails but I don't want this f¥¥kin thing to beat me. The unit is actually working, I just need to find out why it's on all the time.

Pukmeister, I'll give Steptoe a shout when I get a chance to check the wiring around the headstock and ignition, thanks.

And Chris, I'll take your advice, I should have listened to you before

Good luck & hope you can get it sorted, I had the same issues as you but could not get to the bottom of it, tried everything, including completely stripping the unit and cleaning all the gauze filters but to no avail. Prior to my ownership it had always been serviced at main dealers, last fluid change was about 18 months prior to the start of my problems. I thought it was due to low fluid level on rear circuit so changed pads and bled complete sysytem, alas no good, so stripped unit and still had same problem, unit on all the time. 911 codes showing pressure sensor fault and/or rear circuit pressure too high. Fingers crossed for you, if Steppers can't fix it, you know it's fooked!!
Pads

 

[coxy]

Good luck & hope you can get it sorted, I had the same issues as you but could not get to the bottom of it, tried everything, including completely stripping the unit and cleaning all the gauze filters but to no avail. Prior to my ownership it had always been serviced at main dealers, last fluid change was about 18 months prior to the start of my problems. I thought it was due to low fluid level on rear circuit so changed pads and bled complete sysytem, alas no good, so stripped unit and still had same problem, unit on all the time. 911 codes showing pressure sensor fault and/or rear circuit pressure too high. Fingers crossed for you, if Steppers can't fix it, you know it's fooked!!
Pads

No luck with this today. I checked all the wiring loom around the ignition but it all seems ok.
I didn't take the ignition off though as according to the Haynes manual ill need to drill the heads off the bolts holding it in place, then drill out the actual bolts in order to replace them. I don't have a garage or shed so am working outside in the driveway. Don't want to start something I can't fix.

I'm still at a loss as to why the modulator switches off when I disconnect the connector from the front brake microswitch though. i cant help thinking theres something there that I'm missing. That switch is open all the time until the brake lever is pulled to close it. I've had the switch apart and it's working ok. Can anyone shed any light on why that might be happening?

 

[paddy dougan]

Hi Coxy,
I think you'll find that these switches are push to break, ie; current is broken when lever is applied. this is why it stops when disconnected. I'm pretty certain of this, though could be wrong.
Sorry mate but still think the problem lies within the abs unit. Steptoe really is your best bet, if he can help he will.
Chin up,
Pads

 

[Pukmeister]

I thought the brake switches were normally open?

 

[coxy]

I thought the brake switches were normally open?

Thanks Paddy/Puckmeister,
The switch is open until closed by pulling on the brake lever. I spent hours looking over the wiring this weekend but still no luck. Will try to get a bike electrician to have a look tomorrow, hope he has some suggestions,
Thanks again

 

[SteveJ]

My 2004 GS is starting to play up with the same problem; ABS pump continues after the ignition is switched off. Only way to stop it is to disconnect the battery
Ah well, here goes on another 'get to know your bike' experience.

 

[coxy]

My 2004 GS is starting to play up with the same problem; ABS pump continues after the ignition is switched off. Only way to stop it is to disconnect the battery
Ah well, here goes on another 'get to know your bike' experience.

Sorry to hear that Steve. I've taken the unit off the bike, cleaned the filters in it, took off the two pressure sensors and made sure they were not stuck and are moving freely, put it back in then flushed and bled the system but still have the original problem. Looks like I'll be sending it to Module Masters for an overhaul. If you don't have any luck with your own they might be able to help you http://modulemaster.com/rebuilds/shop/abs-modules/abs-ate-abs4/ They give a 5 year warrenty with repaired units.

 

[alex_rsa]

If your bike is 2004 then you have a Generation 1 ABS which is not the one Module Master fix. Motoscot is the only place I found that will fix the older unit and they need the whole bike.

Mine is currently sulking in the back of the garage until I de-ABS it.


Alex

 

[coxy]

If your bike is 2004 then you have a Generation 1 ABS which is not the one Module Master fix. Motoscot is the only place I found that will fix the older unit and they need the whole bike.

Mine is currently sulking in the back of the garage until I de-ABS it.


Alex

Well I removed the ABS unit from the bike, plumbed the brake lines directly to the brake calipers and split the ABS unit to keep the electircal unit and discard the pump unit. All good now, except the brake light is flashing on the clocks, need to sort that out now. Over 1,000 km done and all good
There is a word document that I made up with photos showing the 'servoectomy' step by step but I cant post it here for some reason. If anyone wants a copy PM me with your email aqddress and Ill send you on a copy.
If anyone can advise how I can post it then I'll put it up here for all to see.

 

[bisbee]

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