what vehicles to avoid disconnecting plug

Pretty much says it all in the title. With all of the data options out for cars, it is getting more and more difficult to NOT disconnect module plugs in order to get an accurate pin count or to even see the wires you need (especially those that are behind the fusebox or the BCM on new Nissan PTS). Obviously you never want to cycle the ignition with a module disconnect in fear of an idiot light coming on and never disconnect an airbag module; but has anyone run into any issues with certain vehicles and disconnecting anything? So far I've been ok, but I'm always fearful of something and try to avoid it as much as possible. Obviously disconnecting the battery isn't always possible since you need to test the wires and have to have power to do that. Kenny

Owner / Technician

KKD Garage LLC

Albany, NY 12205

VOLKSWAGEN AUDI PORSCHE SKODA SEAT effectively ALL VAG cars. Then MERCEDES Stay away from French and Italian POS cars. Then TOYOTA. The hard and fast rule is not to turn on the ignition when you have something to disconnect. If you must disconnect, turn off ignition, remove, reconnect then turn on the ignition. Some vehicles NOT VW will recover after running them for a few miles, e.g. Mercedes, Euro Ford (Fiesta, Focus, Fusion/Mondeo/Mazda6).

Sorry I'm misleading you, ALL the above are disconnect safe with the ignition off.

You may have to re-tune the radio presets, or the ECU/EMS may go into a relearn mode... (if their power is interrupted for long enough).

Also, if you are in an area where they do emission inspections, ask the customer if they are going in for an inspection soon.  A recently disconnected battery ( or power interruption to a computer ) can give a "not ready" code.   Some vehicles require many start / stop cycles and/or miles before the "not ready" clears.Soldering is fun!

This is all that's relevant:- The hard and fast rule is not to turn on the ignition when you have something to disconnect. If you must disconnect, turn off ignition, remove, reconnect then turn on the ignition. Or else, carry up to $10K worth of diagnostic equipment or the latest VAG-Com.

Or get EXTREMELY friendly with your local auto electrics specialist, Snap-On, Mac or Bosch distributor! I have a back-scratch arrangement with the first, I install new equipment for him and and get to borrow his stuff!

Yea, I never turn ignition on with something major unplugged. Hell, I even triple check all panels I removed to make sure there is nothing Airbag, etc. related before cycling ignition for testing.Kenny

Owner / Technician

KKD Garage LLC

Albany, NY 12205

Only thing that comes to mind besides Howie's advice, was on a nissan 370zed (too much top gear watching) when i disconnected the driver door panel/switch assembly the windows would not work after putting it all back together. This was all done with the key off and it was plugged back in before turning the key on. Dealer had to reprogram the window control unit. To master and control electricity is perfection. *evil laugh*

I do vaguely remember something about Nissan window controls. But I believe there is a 'work-around' for fixing it. Something like holding the down switch for so long then this then that... can't remember now. Kenny

Owner / Technician

KKD Garage LLC

Albany, NY 12205