Error code 23993 - Pressure monitoring, rear, secondary circuit

[chuckbird]

Hi everybody,

I'm having troubles with my 2010 K25 R1200GS Adventure ABS unit (ABS Integral).
This is what happends in short: the rear brake pedal becomes soft and an insufficent brake pressure is delivered to the rear brake pads.
After using the front brake very hard the red error light lights up on the cockpit and goes away whenever I switch on and off the motorcycle.

The error reported by GS 911 is written in the topic subject: 23993 - Pressure monitoring, rear, secondary circuit.

Bleeding the rear circuit even with the GS-911 ABS Bleed test did not solve the issue because the problem appears again after few kilometers.

After bleeding the brake circuit air bubbles appear in the brake liquid, but there isn't any visible brake liquid leakage from the brake line (nor pump, nor brake pads actuator).

Watching through an endoscope, the ABS module seems to be lightly wet but I cannot understand where is the leakeage.
There is no leakage from the brake lines attachments.
The leakage seems to start from the back of the modulator ECU.

I've also made the ABS output test for all the 4 valves: three of them produce the same "tic" sound, the fourth (Rear Intake Valve) produces a smoother sound.

Any kind ideas?

Thanks in advance for your kind help.

Marco

[Jughead]

Hi Marco

Are you loosing fluid in the rear reservoir?  Does the fluid level drop at all?

Make sure you are not riding with your foot resting on the brake pedal.  This will cause the caliper to overheat and the brake fluid to boil.  This will result in the rear pedal becoming soft, as you describe.

My suggestion would be to bleed the system again to make sure the system is clear of any air.  Then take the bike for a ride again and be conscious of where your foot is.  Make a conscious effort to move your right foot back so that only the ball of your foot is resting on the footpeg.  If you are still loosing braking on the rear after that, it is possible that the rear master cylinder is getting stuck and putting pressure on the pads.

[chuckbird]

Hi Jughead,

thanks for your kind reply.
My problem is due to some troubles that cause air intake in the rear circuit.
I don't put my foot on the pedal during driving nor the temperature of the caliper rises up.
I've tried to do the ABS bleeding many times but the problem still happens after few kilometers, even without press the pedal for activating the rear brake.

There is not any visible leakege in all the brake line but only at the rear part of the ABS hydraulic accumulator, between the aluminium block and the ecu enclosure.
As posted above, when I do the ABS output test through the GS-911 interface, I hear a strange noise coming from the rear intake valve which should be normally opened.
The noise seems to be like smooth as compared to the noise produced by actuating the other 3 valves.
The bad noisy valve is that which closes the circuit of the master pump (the pedal itself) whenever the electric pump runs to compensate the accumulator pressure.

I think that this valve is stuck or is not working properly so it should be a direct consequence of air intake during the normal modulator operations.

The issue happens after few kilometers after a correct circuit bleeding even without using the rear pedal nor pressing the front lever.

[Jughead]

You should not have any fluid visible at the pump.  Maybe check that all 4 pipe connectors are properly tight.  Clean the outside of the pump thoroughly with running water to get rid of the fluid already present, dry it properly and bleed the system again.  If the fluid reappears you should be able to see where it is coming from.

Does the fluid level in the rear reservoir drop?

The difference in the sound of the valve could be due to low pressure or air in the system.