ruf63

Had this happen twice months apart. Start and drive and everything is fine. Hop into the store for a few minutes and start the car and EVERY warning light and buzzer greet me. Try to turn the car off and it will not shut off. Car is running but no rpm gauge movement. 1st time, I drove the car home about 2 miles and the odometer/speedo/rpm did not move the whole time. Finally figured out if I hold the start button down for about 10 sec, the car will turn off. 1st time, made an appointment at the dealer for a few days later and when I got into the car to take it to them, everything was back to normal. Went to the dealer but never actually had it scanned due to a issue with the warranty. Figured I would order up a Ross Tech vcds and figure out what it was if it ever happened again. Ran the codes after the 2nd time but everything seems to be that either codes from faults with other modules or lack of communication. Could just be I don't know what I am looking for in the vcds. Leads me to believe it is a dying battery issue. Any thoughts in the fault report? TIA

Jack88

I can never rule out a battery, but I've never seen anywhere near that many serious codes from a battery. Maybe a water intrusion, something got wet or is getting wet. Do all of your drains function well, ever hear what sounds like water sloshing coming from anywhere? It could also be an issue with a single electrical component, like the ECU. Couldn't hurt to look for signs of rodents chewing on things, since the car is too new to corrode naturally. Damage from other work is also possible.

Short answer, I can't help you narrow it down much, not without some further diagnosis. Try doing an optical loop scan and see what results that gives you. It may help narrow it down to a component, even if not the actual failure.

LexusLSguy

Did you put a meter on the battery? It's worth seeing if it is holding a charge. They can be had for really cheap. Batteries going bad can wreak havoc on these luxury cars.

MP4.2+6.0

Like other replies, I can't be sure. Any real life signs of a fading battery? Slow cranking? Keyless entry not working (one of first things car shuts down that you may notice if it thinks it is low on juice)? There are several places/codes that include voltage where the battery voltage is under 12V, yet others where it looks okay. Without lots of comparison of exact timing of those and what you know from being there/driving it, hard to make sense of why the differences. But from experience, I can also tell you simply running VCDS with ignition on long enough--especially if you dont shut down MMI, tunes, HVAC blower, etc.--will drive battery under 12V in well under an hour.

For now I would clear all codes and see it it returns again. A step further would be to disconnect battery fully and leave it so for a half hour or more before reconnecting. Old D3 idea that sometimes would cure various electrically connected hiccups. If you want to do this, probably proceed first with the disconnect and then erase all codes. Also when erasing codes, re scan right after to be sure the clearing took. Unless Ross Tech finally got it right, often I have had to go into each module with codes and clear individually.

ruf63

Thanks for all the replies. Checked for water "swish" and intrusion and found no evidence of present or past water. Looked for chewed wires and found nothing. Tested down the battery voltage and capacity and everything seems fine with my tester except for the fact that my ctek trickle charger has not gone into float mode after bring hooked up for 2 days. No real signs of the battery being the issue. Starts, cranks and operates as normal. Reason for assuming it is battery related is the amount of codes at once and had an issue in the past with a Mercedes that was normal until the battery went one day while driving. Alarm went off, windshield wipers flying around , radio on and off, windows up and down, etc. all without previous warning. That was a long 10 miles home. Traced it back to a bad AGM battery. Going to replace the battery as I can't find any smoking gun as to the cause. On retrospect, the 1st time it happened, I had had the car in jack mode and had forgotten to take it off before driving. Odd that it would make the car throw that many codes though.

LexusLSguy

Jack mode would not do that. I think the battery is the most logical answer. Any idea how old it is? They don't always fail right away. It can be a drawn out painful process if not properly diagnosed.

ruf63

Had to get to the battery. Week 32 of 2012 or August 2012. I am starting to believe my issues are due to a battery dying a slow death. Get it switched out today and report back.

LexusLSguy

I'm doing mine as well. Even though mine is not bad I'm replacing anyway due to age and I'm a little crazy like that. I originally got Bosch AGM from Amazon but I got the wrong size. I picked up a Varta today from a dealer for $230 and plan on installing later today or tomorrow. Don't forget to code it with your VCDS to reset the battery management system.

LexusLSguy

Any update?

ruf63

No update yet. Replaced the battery but haven't really driven the car too much. Rain and flooding for the last week here and the other car was already dirty. One thing I did notice is that my MMI fires up a lot quicker with the new battery in. Going to switch my wife back to it from my S63 next week. Will report back next week.