BMW R1200 GSA ABS Error ABS malfunction

[Niels Guldager]

Hi all,

The ABS on my BMW GS1200 2008 suddenly shut off when riding in Uzbekistan. ABS symbol alert came on in the cockpit display. Now the bike has lost the ABS function, also after restart and shifting through ABS/ASC. It happened on paved road. The GS911 shows these fault codes:

24052 Electrical System under voltage
23952 front Wheel Speed Sensor: No signal

The front Wheel sensor is perfectly clean and seems well protected by the Touratech proector.

Would anyone know about a common or typical solution to this problem?

Any suggestions would be greatly appreciated!

Niels

[Threewheelbonnie]

Unplug the sensor and check resistance across the two wires. If its open circuit the internal coil is stuffed, you need a new sensor.

Set your meter to AC. Yes AC not DC. Spin the wheel. A good steady voltage is correct. No voltage means big air gap. Big variations mean run out so bearings or dinged polewheel.

Best to do this at the ECU plug as the most common failure is the loom then the sensor head. Probe from the back if you can, pushing pin in not out.

The low voltage is a BMW classic, the settings are so tight to get you into their coffee shops. You need 13V at the ECU so start cleaning up those connectors.

If this is a non servo bike ( what were the Bavarian bunglers smoking that day? ) just ride it. You have full non ABS braking.

Andy

[Niels Guldager]

Hi Andy,

You are the man!

Thanks for this excellent advice - your diagnostic fits the overall failure pattern. Thanks for providing some insight here.

I will work on the bike today and let you know how it plays out. I will also get a new battery installed.

Niels

[Niels Guldager]

OK, went to work following Andy's instructions:

Sure enough, the ABS sensor signal had rubbed against the brake line enough to create visible exposure of copper wires!

I then cut away the bad, exposed ABS sensor signal cable section and re-connected the cable ends - first with crimp connectors and also tried with electrical tape.

However, both errors are still there! I thought I had it fixed since the error condition was so obvious but apparently there is something more going on.

Any suggestions based on this situation? Do I need to do a reset or something?

I got 12.1 V out of the ECU connecting to the ABS sensor signal cable.
What kind of AC reading should I expect? In the low V-range or mV range?

Niels

[*Touring Ted*]

Low voltage codes are common and usually mean nothing.. They happen all the time.

Does the 911 give your frequencies of the code or the last time it happened ??

If the sensor is clean, the clearance correct and the sensor wheel isn't damaged then the 'No signal from speed sensor' fault is usually a faulty sensor. The the speed sensor just means needs replacing in that case.

If a new sensor doesn't fix it then it can be the ABS control unit being at fault or a damaged cable. The ABS control units (pumps) are notoriously terrible on 1200's. And they cost £1500 plus about 4 hours of dealer time.


Like Andy says, it's a none- servo so your brakes will still work. Just put a sticker over the light and tear off the BMW badges and pretend you're riding a reliable, high quality Adventure bike.



P.S. You don't need to reset. The ABS light will go out once the control unit is receiving the correct signal and voltages when both wheels are turning.

[Threewheelbonnie]

An ABS sensor is just a few hundred feet of hair thickness wire with the middle 197 feet wrapped round a plastic bobbin to make a coil. The thin wire makes them sensitive. Try solder rather than the crimps. If you change the resistance from the 10-20 Ohm sort of area the ECU will see it and take its bat and ball home.

When you get home swap the front and rear sensors at the ECU plug. If the fault moves (new code) its the sensor. If it stays put it's the ECU. Usual fault on vehicles with more than three wheels is from where the pin goes into the ECU onto the circuit board. It has been known for careful use of a Stanley knife and soldering iron to avoid having to sell a Kidney or first born child.

Ted, you've just cost BMW thousands. All those "ECU resets" where clearing the error memory has swept the faults under the electronic carpet at £60 a pop

Andy

[Niels Guldager]

Thanks Andy and Ted!

I got the ABS sensor signal cable ends soldered together as you suggested and now the ABS system checks everything OK. Warning lamps act normal and ABS function is back.

So the original error was the ABS signal cable rubbing against the brake line cable between the two first cable support clips counting from the front wheel. This caused a break in the cable leading to the loss of sensor signal.

This design does actually not seem robust - I guess this goes back to Ted's comment about a proper adventure bike. Is there a fix for this?

Many thanks again for sharing your expertise and very valuable advice!

So what is a proper adventure bike?

Niels

[Threewheelbonnie]

Result

Glad you got sorted.

Andy

[Walkabout]

Originally Posted by Niels Guldager

So what is a proper adventure bike?

Niels

That question opens a can of worms or even Pandoras' box.

Cue for another thread!

[*Touring Ted*]

Originally Posted by Niels Guldager

Thanks Andy and Ted!

I got the ABS sensor signal cable ends soldered together as you suggested and now the ABS system checks everything OK. Warning lamps act normal and ABS function is back.

So the original error was the ABS signal cable rubbing against the brake line cable between the two first cable support clips counting from the front wheel. This caused a break in the cable leading to the loss of sensor signal.

This design does actually not seem robust - I guess this goes back to Ted's comment about a proper adventure bike. Is there a fix for this?

Many thanks again for sharing your expertise and very valuable advice!

So what is a proper adventure bike?

Niels

Well my comment was a little tongue in cheek. But its true. I'm a BMW technician by training.

In my opinion, a proper adventure bike is one that is capable of the trip it is intended for. But mainly it should be reliable and simple so easier and cheaper to diagnose and repair. Bikes like your GS aren't really made for hardcore adventuring. Its just good marketing. BMW know that less than 1% of their owners will actually attempt to make it do what it is marketed for. They are dependent on dealer networks, diagnostic computers, specialist tooling and owners with very deep pockets..

The alternatives are vast and varied. Non can-bus is a good start. Gravity fed fuel helps a lot and air cooling makes it simpler again.

Personally I think bikes from the 90's are the golden era. Good engineering with solid state electronics without being needlessly over-complicated with control units, fuel pumps, rider aids, abs etc etc.

The Hubb has a million threads on this topic..

[Threewheelbonnie]

To me it boils down to what you know, what kit you can carry , what functions you need and what support you get on the way.

ABS is semi useful in most places compared to very useful in European cities. The GS911 tool gave the diagnosis and there are people on the net who can work from there. As I work for a company that makes brake systems this wouldn't scare me, plus with ABS as against EBS and servo systems worst case you just put tape over the light.

Totally agree on CAN. Does nothing for the user, needs a laptop to diagnose and ties you to very 1st world suppliers. If Niels had had a non runner and fault message like "checksum error repeat rate or incompatible module" we would still be buzzing out the loom and unplugging stuff.

My comfort zone of technology is between about 1980 and 2005. I don't like the last generation of vacuum assisted, auxiliary butterflied and bypassed carbs and basic FI uses less petrol.

Proper RTW bike? Enfield Bullet Diesel.

What I ride; Moto Guzzi V7, single point FI and electronics you can diagnose with a multimeter.

Andy

[Niels Guldager]

Thanks for your advice!

1000 km later and the ABS is still good - the error is clearly gone!

Niels