Need Help/Advice with the ABS/DSC Trifecta Light
 

I know, another thread on this topic. I have read much of what is out there on this issue. I am looking for advice from those here who seem to know so much about this issue specifically given my symptoms. I have been chasing this down for a while and can't afford to pay the shop with a baby on the way and also have some interesting symptoms which are a little out of the ordinary. I am decently competent shade tree mechanic but do not have a BMW specific scan tool.

First let me give symptoms- The trifecta lights come on at 20 miles per hour or when you floor it. Under this speed everything works normally. I originally though pre-charge pump and ordered a used one. Upon closer inspection I determined it was a bitch to change and made sure to test it first. Upon putting 12v's to the pump it seemed to be working just fine and sounded strong. The car had a $2500 brake job before I bought it at NTB and they did master and calipers I believe. I have no issues with cruise or speedo. My OBC button does't cycle but I think this is the button.

After the pre-charge pump seemed good I sent the ABS module off to BBA reman to be rebuilt. No change. I then replaced all 4 wheel speed sensors (yes with crappy aftermarket sensors) Then in the winter once our roads were snow covered an interesting thing happened. After cycling the ABS maybe 15-20 times the ABS light turned off and just the DSC/Brake light stayed. This time the Brake light was red. Upon inspection I found the brake system to be low on fluid. My working theory was an air bubble trapped in the ABS module that was pumped out after enough cycling of the system and I thought the lights were maybe due to low fluid. Not sure how the reservoir went low but at this point I bled the brakes the old fashioned way. Well I ran the reservoir dry by accident and pumped air into the system. So in to a very reputable Indy she went for a good professional brake bleed using the ABS. I just got her back and have the same symptoms. I don't believe the aftermarket sensors are a problem because the ABS was working properly for quite a while in the winter and always under 20mph before the triefecta lights come on.

I am hoping someone can take these symptoms and pin point a likely next culprit for me. Specifically I am wondering if it could be brake pressure sensor? but I read I would more commonly have the DSC light a long with the brake light but not necessarily the ABS light. Thanks in advance

Is BRAKE red or orange now?

Make sure voltage is steady and around 13.8 and steady doesn't drop when you come to a quick stop. A low voltage dip even once will set trifecta.

Misaligned speed sensors also can cause the trifecta so it could be worth checking them. I used knock off abs sensors on my X5 without a problem


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Thanks for the ideas Andrew, I'll check the voltage. All lights are orange, only come on at 20mph. Always start with no lights

Steering angle sensor?

You have a scanner. What is it telling you?

I do not have a scanner

Then stop wasting money. Without a scanner you are setting money on fire.

Your best bet is to get ISTA working. I just diagnosed an identical fault on my other BMW. In my case, one of the ABS sensors had failed. The bad sensor appeared to be working but every now and then it'd send garbage data and cause the computer to think the car was in a full on skid causing ABS to activate etc.

I diagnosed it by asking a friend to drive the car while viewing the live data - one wheel suddenly looked to go from 30 to 0 then to 60 then to 0 then after a few seconds it was all good and in agreement with the other three wheels.

Not saying this is your issue, but seriously without a scanner I'm not sure why you'd pay to send stuff to BBA without actually verifying the fault!

Take it for a drive with your laptop running ISTA hooked up to it. Check that all 4 wheel speed sensors are in agreement. Then check the live data coming from other parts that influence ABS/DSC (steering angle sensor, vehicle angle sensor etc).

:iagree:

Don't want to spend the money, or take the time to learn, then take it in. Without any type of data as to what the system is doing it is just a WAG (Wild Ass Guess) on everyone part.

Sorry. I misread your post. As others have said, you're wasting time and money trying to diagnose this problem without a scanner. there are Chinese made ones that run about $75 and there are those made by Foxwell which run $150. In my experience the Foxwell units work better than the Chinese ones. If you're planning on wrenching on your bimmer, then you need a scanner. Spend the $150. It will be the best $150 you ever spend and save you from throwing parts (money) at a problem.

Like others, I highly encourage you to buy Scanner first before spending anymore onto it.