Would the steps be the same or similar on the air cooled alternators? I think us I6 guys have the non-watercooled one

I would think the I6 aircooled alternators are DIY rebuildable also, I haven't looked into it.

Well got the X back from the Indy but still have the trifecta. The only Auto-logic code left is 117 Brake-light switch (line). The brake light switch has been replaced and the fault is intermittent. We assume it is the module that needs rebuilding, does this make sense?

Thanks again guys!

Mike

If you haven't rebuilt the module yet its a good place to begin

So, I replaced the alternator, using a reconditioned Bosch AL0703X [BMW -599 p/n]. While in there, I replaced the power steering reservoir and drained/replaced the fluid. The problem with this task is getting to the banjo bolt at the rack, its up above the metal protective cover. I used the ebay 32mm fan clutch tool, a good $17 [plus shipping] investment. Unfortunately, charging the battery [an 18 month old interstate] while doing the alt install, it appeared not to take/keep a charge, confirmed when I tested the alt and battery on the meter at my local O'Reilly's. I supposedly have a 30 month free replacement warranty on the Interstate, we'll see. If not, to Pep Boys for the Bosch. Still showing the trifecta, even without the tell-tale click, which I hope is alt/battery related, for the moment. Fix one at a time, I suppose ....

My alternator is spot on, never dips below 13.4v, and the Bosch batt must still be running strong too. I have a feeling I need a DSC pressure sensor or brake light switch from the intermittent error I still am throwing. But at least I know the module is good to go now, lol

That sucks. I'm surprised the interstate didn't hold up. My buddies shop sells them and I never hear of them coming back under warranty. Hopefully it's the battery this time around.

Actually, on retest at the Interstate shop, the battery showed 759 cca and 12.43v on the meter [18 months in to the 30 month free replacement warranty]. Operator error on the multimeter at my local O'Reillys on the earlier test [it pays to doublecheck these guys; I suspect the machines are pre-set to say 'bad battery' to motivate sales .....]. I replaced the gear in the transfer case actuator yesterday afternoon and no more 'trifecta' with that and my having replaced my alternator with a Bosch rebuild from autohausaz ....

FIXED as of May 2015
 

Naz, you can mark the thread title as fixed and I am bumping it to help out others.

Long story short, use DIS scan tool. In the last 2 years the intermittent trifecta which would come on, and reset at the next drive cycle was cumbersome but didn't really effect me. About a month ago I wanted it gone for good.

I sent my ABS module for a rebuild (prevenatively and I thought it might be my issue) and after receiving back I had received 2 random trifectas since then. So I hooked up DIS. THE ONLY CODE I HAD ON MY ABS MODULE was 2 codes for Brake Light Switch.

Bought a new one from the dealer, installed on Saturday morning 2 weeks ago and installed. Has not been back since.

In my case the trifecta was a Brake Light Switch ($33) from BMW needing replaced.

Hi guys. Read through this thread and others in relation to my '04 4.8is w/80k.

The trifecta came on after replacing my battery (always on, never intermittent). I never heard any clicking or noticed any effect on drivability. Indy rebuilt actuator and replaced/programmed transfer case module which cleared some related codes but their scan still shows fault to transfer case. Any possibility the transfer case is not the issue? Could it be the DSC/ABS control module or a sensor?