what vehicles to avoid disconnecting plug
Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=133886
Printed Date: May 15, 2025 at 1:44 AM
Topic: what vehicles to avoid disconnecting plug
Posted By: offroadzj
Subject: what vehicles to avoid disconnecting plug
Date Posted: March 18, 2013 at 5:59 AM
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.
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Kenny
Owner / Technician
KKD Garage LLC
Albany, NY 12205
Replies:
Posted By: howie ll
Date Posted: March 18, 2013 at 6:16 AM
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).
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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.
Posted By: howie ll
Date Posted: March 18, 2013 at 6:18 AM
Sorry I'm misleading you, ALL the above are disconnect safe with the ignition off.
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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.
Posted By: oldspark
Date Posted: March 18, 2013 at 7:05 AM
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).
Posted By: kreg357
Date Posted: March 18, 2013 at 7:37 AM
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.
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Soldering is fun!
Posted By: howie ll
Date Posted: March 18, 2013 at 7:47 AM
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.
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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.
Posted By: howie ll
Date Posted: March 18, 2013 at 7:51 AM
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!
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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.
Posted By: offroadzj
Date Posted: March 18, 2013 at 9:17 AM
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.
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Kenny
Owner / Technician
KKD Garage LLC
Albany, NY 12205
Posted By: racerjames76
Date Posted: March 19, 2013 at 12:38 PM
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*
Posted By: offroadzj
Date Posted: March 19, 2013 at 1:05 PM
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.
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Kenny
Owner / Technician
KKD Garage LLC
Albany, NY 12205
Posted By: pts760
Date Posted: March 19, 2013 at 1:27 PM
On all Scion/Toyota's and Dodge Caravan's I always unplug the knee bolster air and cycle the ignition with no problems. FYI
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I drink current, eat ohms, and bleed voltage
Posted By: pts760
Date Posted: March 19, 2013 at 1:28 PM
sorry i meant airbag not "air."
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I drink current, eat ohms, and bleed voltage
Posted By: offroadzj
Date Posted: March 19, 2013 at 2:19 PM
Do you disconnect it with the battery disconnected then reconnect the battery or you just unplug it? The knee bolster airbags are constantly a PITA. Luckily on the Avalon I just did, there was enough wire that I could set it on the floor (on some padding to keep the panel from getting scratched) and had enough room to work. But the Chrysler's are a royal PITA
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Kenny
Owner / Technician
KKD Garage LLC
Albany, NY 12205
Posted By: pts760
Date Posted: March 19, 2013 at 2:26 PM
I disconnect and reconnect them with the battery connected. I've done work for the local dealership for around four years, done hundreds of these vehicles, and have never had an issue.
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I drink current, eat ohms, and bleed voltage
Posted By: pts760
Date Posted: March 19, 2013 at 2:30 PM
The airbag lights do reset once the airbag is reinstalled without a scan tool.
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I drink current, eat ohms, and bleed voltage
Posted By: kreg357
Date Posted: March 19, 2013 at 4:53 PM
Kenny & RacerJames, here is a possible fix on the Nissan power windows posted by another forum member ( never tried it myself ) :
Nissan / Infinity Power window reset
1. Window reset
A: Hold switch down to FIRST stop (not auto), roll window all the way down, keep holding for 5 seconds.
B: Push switch further to the AUTO DOWN position; hold for 5 seconds.
C: Pull switch up to FIRST stop (not auto), roll window all the way up, keep holding for 5 seconds.
D: Pull switch further up to AUTO UP position, keep holding for 5 seconds.
Worth a try before going to the dealer. ------------- Soldering is fun!
Posted By: howie ll
Date Posted: March 19, 2013 at 5:20 PM
That fix to my knowledge seem to work on the following:-
VW
Mercedes
Toyota
Euro GM, Vauxhall Opel + Saturn Astra, Buick Regal
Euro Ford
But funnily enough not BMW.
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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.
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