which dmm do you use?

Point taken, hence my point about using a test light. I mean take a Toyota, any Toyota, how many of those wires at the plugs going into the doors are likely to be data? Caught myself there some Japanese e.g. Mitsubishi use data on the window circuit from the driver's door to signal up/down to the satellite switches.

Data - now that's a different issue. Definitely in scopesville or probesville there, except for fast analog types.

When I use a DMM, it's this vintage ( 1980's ) Fluke 77.  More accurate than needed, no Frequency setting and a bit large but I'm still using a WEN soldering gun from the 50's...  

Soldering is fun!

It the OP thinks his 117 is fast, he has never used a 10, 11, 12, 16 or 18. These are the bottom of the line Fluke meters. but are by far the best engineered meters in their lineup. I have several 87s, and the only time I use one is for the high resolution resistance setting. I use my 16 EVERY DAY.

Kreg, please tell me that's not your new kitchen work top...... Peter a mechanic once told me that one CAN (do you like that one) do data via a DMM but I think along with the one about the locksmiths who re-write the vehicle software to negate the immobiliser system (instant by-pass) it's an urban myth. OP: also remember Mr. I along with Oldie and KP is an electronics man so when five of us now come out with the line about not needing super gear on a car, do you not think there's something in what I said about only needing cheapo meters. HEADS UP!! the latest BMWs use a "sniffer circuit" at the battery. Do not ground any equipment to an existing brown ground wire, use a chassis bolt. The damned thing is over-sensitive 12.4V or less and the ignition won't work. Bloody fussy over engineered German cars. Why?

LOL - BMW 12.4V? What about when they are cranking - surely that <12.4V must be disabled!? But to think my 12V car cranks AND ignites with a 5V battery (5.2V to be exact) - that exceeds even my usual "down to 8V" designs. So Kreg's got "my" Fluke eh? Envy+ I have often noticed how my electrical/electronic gurus have the most basic of equipment. Rarely do they have purpose built or expensive stuff, though spectrum analysers are an occasional exception (for the "noise" gurus). But DMMs etc are usually el cheapos like me. Or the odd Fluke. And the audio guys have Wattmeters, else use ONLY true-RMS voltage if they merely test into resistive loads.    

That's the whole point Peter, it "sniffs" the voltage BEFORE it cranks.

Then I'm with you... the logic being...????!! Are they trying to preserve the battery? IE - they'd rather leave you stranded somewhere and possibly die rather than cause more than usual strain/damage to the battery. Or are BMW electricals so bad that they are damaged by undervoltage? IMO both are reasons NOT to buy a BMW - unless you only drive in places with full facilities.

Plus on star in the US, or who doesn't have a cellphone in the UK? Gets you straight back to the stealership. = $$$ And they use just about the biggest car batteries ever.

Alas here it's very possible to be out of cellphone range - especially of on Vodafone LOL!. I'm not surprise BMWs have big batteries. With 400A cat converter pre-heaters, and 12.4V thresholds. But yeah, a typical money grabbing technique - and you know how much I love that. But back to DMMs...