Emerg Trans Failsafe

[mchlkly]

I have an ’03 X-5, 3.0l e53 with 225,000 miles. I’ve been using after market inexpensive MAF sensors .

When the MAF sensor fails the car will go into Emer Trans Failsafe mode immediately on start -up. Put in a new one, wipe codes and the car will drive perfectly for about 20 miles then trigger the trans mode, not full limp home mode, just a slightly reduced transmission performance.

It’s throwing a lot of codes but I can’t see which is triggering the trans mode. Since performance before the mode is triggered is perfect I’m assuming there is a bad sensor elsewhere, perhaps temp related that’s causing this. Any one seen anything like this? Suggestions on what could be causing it?

If I shell out for an OEM sensor would it help?

[Effduration]

So the 6-cyl X5 only used the 3-pin MAF thru it’s entire run.

I’d suggest you go find a used OEM/Siemens one in a junkyard and try it.


I did this for an X3 (6-pin MAF) and it made a huge difference.

[Clavurion]

Sounds strange that a failed MAF alone would cause trans failsafe. What are those other codes?

[workingonit]

Originally Posted by mchlkly

I have an ’03 X-5, 3.0l e53 with 225,000 miles. I’ve been using after market inexpensive MAF sensors ...

If I shell out for an OEM sensor would it help?

I (also) have an '01 X5, 3.0i E53 with 211,000 miles. I've (also) been using (an) inexpensive MAF sensor...

(I've also wondered) "If I shell out for an OEM sensor, would it help?"

I'm not so sure if it would've helped to eliminate my (formerly) recurrent P0171 & P0174 codes (with the Check Engine Light getting triggered), but I was just about to buy one, just to see, but didn't have to.

My codes followed the same sort of pattern your X5 has done, except for different coding. On mine, it was not obvious that the MAF (an OEM Siemens unit, clean and in good shape) was underreporting, but after I tried a cheap MAF from Amazon, then the fuel trims started to balance, and my 6+ month-long hunt for the problem source was ended. I'm not completely sure there's not a tiny vacuum leak still hidden. But the X5 passed emissions in October, and is still purring along.

Not knowing what codes you're seeing, or whether or not an O2 sensor might be iffy, there's no way to guess if an OEM quality MAF would help you out, but again, in my case, I took a chance on a $23 MAF (as recommended by X5chemist), and it worked. I might've not gotten any better results buying a $250-$350 OEM part ???

Coincidentally, I just got another cheap MAF from Amazon (now $21), instead of getting a refund for a cancelled order, so now I have a brand new spare, for 2x the price of a can of MAF sensor cleaner.

Post some data so others can analyze your problem (better than I), but perhaps it'll be something simple.

[X5chemist]

workingonit's MAF is same one that's been in mine for over a year. I took out the OEM to clean and installed the temporary MAF. Since it's been working fine, I've left it alone. City MPG is ~16 city. Highway MPG has reached as high as 24 true MPG.

Post your actual codes. Someone may have a history on them. Plus, it's known the harness has issues with water.

[mchlkly]

I looked for an OEM MAF sensor the last time I was at the recycling yard but came up empty. I agree that's a good idea.

Anything in this array look like the problem?

Thanks for all advice, I really appreciate this forum.

[mchlkly]

[Henn28]

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.

[mchlkly]

Thanks, Henn28, I hadn't considered that and it sort of fits; the hub takes so long to come up to temp while under way then triggers.

That bit about the air conditioning and camera is great. To every car its own gremlins.

My battery is old and is probably a factor but that wouldn't reliably trigger at the same place on my commute. I'll replace that. Would failing to register/initialize the previous battery be yet another weight on the Trifecta scales?

I have replaced the ATF and cleaned the harness. I'll look at the brakes, the abs light has been on since I bought it off craigslist 7 years ago. If it's an expensive mess it could be why I got it so cheap.