Persistent DSC Unit Calibration Failure (ISTA)

[patroklai]

Hey guys, some months ago I went down the path of trying to firm up my brake pedal.
I think it all started after boiling brake fluid during a very aggressive BMW cruise.

Since then, I've installed ECS SS lines, ECS bronze guide bushings, replaced the ABS pump/valve unit (reused dsc module), replaced brake booster, master cylinder, rotors, and pads. I would describe pedal feel as follows: first inch or so is light/feathery (offers little resistance), but I can still feel the brakes being applied. After that first inch, the brake engagement is VERY aggressive and the car stops on a dime. So breaking power is not an issue at all, but rather that first light/feathery pedal travel area that offers very little resistance. I've come to accept that's how our cars behave with these floating calipers.

That said, the biggest issue currently is that I can't seem to get passed the dsc calibration. Previously, I was able to get passed the pressure sensor test but would then fail at the dsc calibration due to "leaky brakes." I'll state now I have absolutely no leaks. However, as of my latest install of a new master and extensive bleeding sessions, I can't seem to get passed the pressure sensor calibration. I did do a test drive earlier and pulled code 5e5e for the brake pedal switch. I cleared it in ista and it didn't come back. I'm wondering is that's causing the calibration to fail. Anyways, wanted to get this out there in case I'm missing something or anyone else has some ideas.


I bled the system at all fittings (bench bled master), and the pedal is very responsive without spongy feel. However, the travel is quite pathetic as my wife's infinity SUV has like 3mm of pedal play before the brakes are applied.

Thanks.

[patroklai]

False alarm. Ended up adjusting the brake pedal switch sensor. All good now.

[Redd]

Originally Posted by patroklai

False alarm. Ended up adjusting the brake pedal switch sensor. All good now.

Glad it's all fixed finally! How did you adjust the pedal switch sensor? I wasn't even aware it could be adjusted. Did that also fix the long pedal travel?

[patroklai]

You can pull the contact point between the sensor and pedal simply by pulling it. The long pedal travel I think is just how it is. Despite the initial pedal travel being "easy," there is definitely some decent clamping happening on the brakes. I just don't think the pedal feedback is a good indication of how much force is getting to the brakes. Maybe it's my ceramic pads with deceased initial bite or just by design. But once I get to a certain point, the pedal grab is very aggressive and will lock up the wheels easily.

I think eventually I'll go to a BBK with fixed calipers and jump off this floating caliper design.