background:
2010 E92, RWD, manual, no iDrive, base stereo, just over 100k miles. currently wearing winter wheels and tires with no pressure sensors, so TPMS light is illuminated. we do this every winter, no issues.
situation:
2 days ago, first start and drive 100% normal. 90 minutes later, on startup, several warning lamps flashed in sync with the warning chime (definitely BRAKE, ABS, and Stability Control, plus Service Engine Soon, maybe others i don't remember), tach dropped to zero and both speedo and tach went dark. This repeated a few times at an interval of a few seconds. Engine was idling the whole time. So I keyed off, waited a few seconds, restarted, and everything seemed fine.
This morning, i started the car and let it idle while i brushed snow off the roof. when i closed the door i heard a single warning chime, which i thought was unusual. looking through window, i didn't see the cluster doing anything strange, but i opened the door and took a closer look. nothing weird. so i closed the door and again i heard a single warning chime. again i look through the window and there's nothing unusual on dash.
Drive to work, no issues. Park the car and look at odometer, and the tamper dot is on. WTF?
I think your first step here would be to get the BMW codes.
You probably had the CANBUS down and it generated a mileage discrepancy between the cluster and the ECU.
Any water got in the car by the footwells? Not sure where the modules are on that car, maybe in the trunk where the spare tire would be? Does it have a sunroof?
With ISTA you could hook up the laptop and check all the modules and it would tell you if any are not communicating, like so:
What kind of shape is the battery in? Our Merc will freak out if the battery isn't good.
Usually the first step in troubleshooting a BMW is to replace the battery, even if it is starting the car and seems okay. The tamper dot shows up when the cluster mileage doesn't match the value stored in the backup data center (it's the IKE module in the E46s, aka the headlight switch.) For an E46, to get the tamper dot off there, the IKE would need to be re-coded. Not sure if E9x are similar.
Edit: Has it had the recall performed for the positive battery cable connection at the front distribution block? One of the symptoms in instrument cluster 'flickering.'
BMW recall - Positive power distribution block
The situation to fix the mileage dot is gonna get either complicated or expensive or both. May have to live with it.
Aaron_King said:
What kind of shape is the battery in? Our Merc will freak out if the battery isn't good.
I'd look into this as well. Modern BMWs hate hate hate low voltage situations, and can make the car do lots of funky things.
Verify the integrity ie not "is it bolted down" but is it functional the battery ground at the trunk stud by removing the trunk filler panel.
Check voltage drop from batt + to the jumpstart lug under the hood.
Pull codes and report back
TPMS module E36 M3 the bed. whiskey_business correctly identified CANbus corruption, internet pointed me to TPMS as most likely candidate.
unplugged module and dash went right back to normal. Plugged it in again and dash wigged out again. After turning the problem on and off a few times, I chucked the module and taped up the connector. I live without TPMS for 6 months out of the year anyway, not gonna spend $350 on this dumb-ass thing when a tire pressure gauge is $5.
You can code out the US TPMS and switch to the Euro TPMS which uses wheel speed sensor instead of the tire pressure sensors. That way you won't have to deal with the light at all; it might not be as accurate but should still turn on if a tire start going out. I had a remote tuner do the coding on my E90 for under $75 if I recall correctly but should be doable with ISTA etc if you're proficient with it.
Ugh. Can't help you at all but sending moral support. I have an older Merc that always has some dash light on for something. I never knew there was even such a thing as a tamper dot.......now I have something else to look forward to.
In reply to AngryCorvair (Forum Supporter) :
You can probably get a used module on ebay for cheap. No need to get a new one.
I appreciate all the suggestions, and I did follow a couple of them.
Battery is an Interstate that was made 11/20 and installed 1/21.
All connections are clean and secure.
Battery test showed 12.4V and 680 CCA
Google told me about the TPMS module, and YouTube had a couple videos of dash wig outs caused by the TPMS, so that's where I started.
Only showing 100k.
Tell me more of this blatant odo tampering you've managed to mask and hack. 
In reply to John Welsh :
LOL. I've clearly been sitting on this info for a while, as there's no way she only had 71k 19 months ago.
