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Henn28 · #8 04-06-2023, 09:15 AM

I'm no expert on the Trifecta (battling one myself right now), but your ABS/DSC codes stand out to me. My Trifecta happens as the car warms up (after about 5 or 10 min of driving after which the DSC module stops communicating with the CAN bus ("DSC Brief Power Interruption" code, live data before, nothing after...its like the module has been unplugged). The Trifecta pop (red brake light, most of the time), the transmission goes to failsafe mode, the AC stops working and interestingly my aftermarket Boyo backup camera stops working (via my Kenwood unit). My X5 didn't have an OE camera, or NAV, etc. so I'm not sure how that failure is happening. I also get a lot of other CAN Bus related module and sensor codes and issues that I think are secondary failures.

Oddly, after my car fully cools down it generally works fine for 5 or 10 minutes again, then rinse and repeat. This is convenient because I can read live data with my scanner before it craps out again.

Can you pull any live data whatsoever from the DSC module, like the wheel speeds power, steering angle, etc.? That may help narrow it down. For example, on mine all the DSC live data looks normal when the car is cold so I'm pretty sure its not a sensor, etc. When it dies however, its like the DSC is suddenly unplugged and everything DSC related goes away. Lots of other codes, but I think they are secondary failures due to the power supply failing in the DSC module. Maybe a grounding issue, perhaps a short that occurs as the unit gets hot.

Also, this is likely way too easy, but I've heard that low alternator voltage can pop the trifecta, and low voltage will definitely cause all sorts of other spurious gremlins and codes.

I've been researching options for DSC modules, and while new are available still, they are super expensive. So for me it will likely come down to used and take your chances, or get mine (or another used one) fixed by one of the many module repair shops on line. Module Masters keeps coming up but there are some complaints I've read, along with several posters saying they did a good job.

Finally, FCP sells a DSC/ABS repair kit for the 3 series X drive cars of our era, which seemingly used the same Bosch 5.7 DSC/ABS module. Its not cheap but may be a solution for me if it will fit, and can be re-programmed. I've asked FCP for info but will only do this if I can determine it is definitely the module and not the pump(s). I'm not averse to throwing parts at my car, but these new modules are just too expensive to go that route without being very sure.

I'm hedging my bets right now and buying a cheap used unit, complete with pump) from ebay that (I think) matches my vin/year, etc. so I can swap it in for a quick fix. Then I'll send my OE piece out to get fixed to have a spare on the shelf.

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