Abdub

Hey all, so about a week ago I was driving my 2000 GS300 home and I made a turn (not one that was particularly sharp) and all of a sudden hear this constant high-pitch beeping. It sounds like it's almost coming out of the speakers and is not any type of "mechanical" noise (obviously an indicator noise). Also at the same time, a CEL was triggered, my parking "BRAKE," ABS, VSC, and VSC OFF lights were on. I carefully drove home and the brakes still felt pretty normal.

I check the codes being pulled and the CEL seems unrelated (however occurred at the same time) which is: P0446 Evaporative Emission Control System Vent Control. I also see 4 ABS codes being triggered: C1251 Pump Motor Circuit Malfunction, C1252 Hydro-Booster Pump Motor, C1256 Accumulator Low Pressure Malfunction, and C1223 ABS Control System Malfunction.
Anyway, I looked up the issue and the brake issues are probably somewhere in the brake system (that statement seems redundant but it is for clarification). I disconnected the battery for 30 minutes and reconnect it and it removed the CEL (the codes still being pulled) but the brake lights/buzzing all remained. Brake fluid level is still normal, no leaking whatsoever. I get in contact with my mechanic and drive it over there...and on the way to his house the lights and buzzing all go off. Regardless I still took it to his garage to be checked out. My mechanic is an extremely seasoned BMW-certified mechanic who early in his automotive career he actually worked on Toyotas at a dealer. He said the codes were cleared and he did not know what to do.

Anyway, I picked it up the next day and drove it home. I then drove it to work and back home, no issues. I then drive down to the lake and on the way, the brake lights/buzzer go back on. I start immediately driving home and when I pushed the brakes down to the floor, they hardly stopped the car and they felt very strange. I've been at a point of indecision with the problem/car and have not touched the car until today...I decided to drive it around the block with the brake lights/buzzer on. So I take my spin and about 5 minutes into it (guess)...all the brake lights/buzzing stop. The brakes felt relatively normal after the lights went on, except my pads were skidding against the rotors on turns.

Mostly I've read when these combination of ABS codes are going off it is your Master Brake Cylinder. However, it being intermittent (I feel like a Master Cylinder failure would be a constant problem and my brakes would not work at all) I believe it's some gremlin in the ABS electronic system. My brake fluid is normal. I haven't had any work done on it in months. At the expense of not wanting to put that much more money into this car, I've been doing research. One of the big things I've read was that the ABS sensor could be shorting or not fully plugged in. This would especially make sense since this all started when I came out of a turn. I'm just curious how one would go about testing something like that. I have not tried removing the ABS ECU nor the ABS fuse yet, two things I'm going to try to see if it does anything.

Does anyone have any suggestions on checking the ABS sensor lines or have any other suggestions for me? I would appreciate any help, thank you!

corkycal

iTrader: (8)

I belive this this may be your problem if you hear buzzing since the accumulator is trying to pressurize the brake system. I hear you are able to recharge these but not sure.
Do a search on this and read more about it.

C1256 Accumulator Low Pressure Malfunction

bilgen

iTrader: (3)

A lot of people with 98-00 2GS's swap their BMC assembly out for a 01-05 assembly due to weird issues like you're explaining. But if I was in your situation I would flush all the old brake fluid out and replace it with new and bleed the brakes. I did this in my 01 when I first got it (had the ABS, VSC, VSC OFF lights on) as well as swap front rotors and pads and all my lights went off. If that doesn't help THEN I'd be on the look out for a newer BMC. Good luck