I was driving up a small hill and gave it a little punch - heard/felt a "clunk" towards the rear and the BRAKE, ABS, BATTERY and ASC/DSC lights all came on. As expected, it began driving in high gear only (Limp mode) for the mile home. I shut it off in the driveway, turned it back on, put it in reverse and after 2 feet heard a similar "clunk" from the rear of car. Thinking it could be the ABS Module? Or?
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The ABS module is under your hood, not in the rear of the vehicle, right?
What codes do you have?
Does anything look physically out of place/odd when you get underneath and look/poke/feel around?
First, first, first, first thing to check is, believe it or not, your alternator and/or battery. The transmissions on these cars are very voltage sensitive and when the tranny senses low output voltage from the alternator it throws the tranny into limp mode.
Read on:
https://www.bimmerfest.com/forums/sh...=602926&page=2
Pay particular attention to post 37 onward.
Interesting enough, I went out to get in it this morning and the battery is dead. I'm going to check that today. Thanks!
Dennis G01: Right - I'm thinking the "clunk" sound was just the tranny acting up but may be caused by? (I saw a thread that seemed to list the warning lights that came on as potentially the ABS module, but only a thought at this point). As crazy4trains mentions below, and because my battery is now dead, I want to at least check into that first. Thanks!
I agree with the warning lights vs ABS module scenario... however the battery light would not normally be apart of that scenario. I don't think the ABS scenario (search for "trifecta") would cause a clunk, though. The ABS is your braking system, not the transmission.
I'm curious to see how an alternator that isn't charging causes a clunk in the rear end, though? Unless it was actually at the transmission and you just thought it was the rear end. Or maybe that's just where a tranny clunk manifested itself - through the driveline at the rear diff.
Once you get the engine running - check voltage with it running. You should have 14-ish volts if the alternator is working. If not, first check wire/cable connections (alt, battery, grounds, etc). They need to be clean and tight - you don't want to replace an item if all that is needed is cleaning/tightening things up.
DennisG01: Yep, going to check that when I get home. The entire battery compartment, wires, connectors, everything literally look brand new. Not a spec of dust or dirt, so don't think it's that. According to a thread by crazy4trains (link in his reply in this thread, above) he experienced the same thing - sounds like the tranny was "locking" into limp mode, causing that "clunk" sound... like the tranny, when it doesn't get the right juice from the alternator, goes into this mode. He explains after post 37 in that thread. https://www.bimmerfest.com/forums/sh...=602926&page=2
I dont' think it's a clunk in the rear end. Don't know it for fact but I think the clunk referenced (also look at post 37 in my above referenced thread) is the transmission downshifting into a lower gear. As you said, it's felt in the driveline somewhere due to the rapid downshift.
Last edited by crazy4trains; 12-18-2018 at 02:10 PM.
crazy4trains, I agree... that's more what I think it was as well. I think, in my head it sounded like rear but was more likely beneath! Anyway, I jumped it today, started right up and only the battery indicator was on, not the other lights AND it was able to go into manual shift mode (it stopped dong that in limp mode). I didn't have time to drive at all and don't want to until I can check the alternator. One curious thing - the key/remote doesn't activate the locks now. Any ideas or connections your can draw? Thanks again, you're being incredible helpful!
Last edited by rgabsa; 12-18-2018 at 07:08 PM.
Are the battery connections also TIGHT?
Do you have a voltmeter? It'll only take a second to check the voltage at the battery. If it's good there, it'll be good everywhere else. If it's not, then start backtracking.
How old is the battery?
Not sure on the FOB - does it maybe have to "re-learned" to the car because of the voltage loss? There's a process that is outlined in the manual.
I was thinking the exact same thing about the FOB. Very possible. I look at all records (previous owner had every single one) and it had a rebuilt alternator installed 10 years ago at around 70k ( now has 138k) and the battery was installed November 2011. I’m having it all checked in the morning at a place less than a mile away, assuming it drives correctly right away. Question: if it does need one, do you think it’s a must to get a brand new Bosch alternator or is a rebuilt one OK ( seems like the one it got 10 years ago lasted pretty well). I only paid $2400 for the car and it won’t be driven much each year (maybe 5k) so I don’t know if it’s worth the extra $$, especially knowing I have a few other things to do to it over the next couple months.
A good rebuilt alternator, in my opinion, is as good as, or better, than anything new. On the flip side, I wouldn't be putting a cheapie/junk alternator on there as I would want to lessen the chances of dealing with it again. For batteries, I wouldn't get anything but Deka or Interstate.
I think it all depends on the place doing it. There's a local shop around me that has been doing this for decades. The people around here that know about that shop won't even consider buying a new one. It all comes down to it being a "good" rebuilt - gotta do 'yer homework.
Or, it could be that most people don't know where to look or who to ask. Smaller cities - sure - most definitely it decreases the chances. BUT, it doesn't negate the notion that a rebuilt can be as good as, or better. I'd be surprised if Atlanta didn't have at least a few good, reputable rebuilders.
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