Why does everybody do this???

blacknblue2002 · Dec 11, 2007

I know that the answer to this is probably really simple and I'm going to feel dumb when it's answered but I searched and didn't see any explanations so...

why do all of the instructions to just about every part installation tell you to disconnect the battery before starting???

For instance...why do you need to disconnect the battery when you're just swapping out your intake plenum or throttle body???

does something get reset when you unplug power from everything???

and if so...are we supposed to re-tune the car after the battery has been unplugged every time (talking about w/ the x-cal 2)???

darkside03gt · Dec 11, 2007

most of the time its to make sure you dont accidently shock yourself other times its to reset your computer

CobraRed_96_GT · Dec 11, 2007

with an x-cal 2 you need to unplug the battery AFTER flashing the tune to let the ECU reset with the new tune on all pre 98 eligible cars. This is also recomended but not nessary when doing it to a 98 and up. All instructions ask you to unplug the batt when dealing with anything electric to prvent a short on something metal in the process, and also to let ur ECU reset like if your now using a speed cal. Or dealing with the TPS sensor which relaies heaily on voltage readouts

4.6andSlicks · Dec 11, 2007

Sometimes they don't want you to set off the airbags. That's a bad day !

blacknblue2002 · Dec 11, 2007

edit:::

thanks for the replies...that answers everything

CobraRed_96_GT · Dec 11, 2007

blacknblue2002 said:
I've heard 'reset your computer' before...but that scares me into believing that I should re-tune the car w/ my xcal after every little mod I make.

is that accurate, or do I have something wrong?

when you reflash your computer it's like loading new software on your desktop. It will from now on use that software always untill new software is reinstalled. But you dont want to work on your computer while it's running right? so you shut it off (in this case unplug it's power source) change some things then turn it back on. It will still use the previous software tho

katshot · Dec 12, 2007

The reason is real simple. They don't want you to accidentally cause an electrical short while doing whatever it is you're doing.
Not sure about Mustangs but all the GM cars I've done re-flashes on DO NOT require the battery to be disconnected at any point.

5spd GT · Dec 12, 2007

It is mainly for the safety of yourself and the electrical system.

CobraRed_96_GT · Dec 12, 2007

katshot said:
The reason is real simple. They don't want you to accidentally cause an electrical short while doing whatever it is you're doing.
Not sure about Mustangs but all the GM cars I've done re-flashes on DO NOT require the battery to be disconnected at any point.

nessesary for 96/97 mustangs for a reset, suggested on 98+

2002GreyGT · Dec 13, 2007

Probably to help idiot-proof the instructions...

But no matter how idiot proof instructions are, there is alway a bigger idiot out there.

I just hate it that I need to reset my radio stations / settings after doing it.

~K

Twista · Dec 13, 2007

^^ i can unplug my battery for an hour and my radio stations are still stored...

Also, i unplug the battery when fooling with the passenger side header bolts. Sometimes my socket slips and his the starter and makes a big spark.

2000fordstanggt · Dec 13, 2007

Twista said:
^^ i can unplug my battery for an hour and my radio stations are still stored...

Also, i unplug the battery when fooling with the passenger side header bolts. Sometimes my socket slips and his the starter and makes a big spark.

after you unplug the battery from both cables touch them together to discharge anything left in the system.

like said before they have to make sure and cover their ass, so nobody says "well how was i supposed to know it would fry my ecu"

chuck943 · Dec 14, 2007

As the old saying goes "Knowledge is what you get when you read the instructions, Experience is what you get when you don't"

jprovence · Dec 14, 2007

this "rule" was recommened way before ECU's. Yeah, there was a time when cars didn't have a computer runing the show. It is to prevent shorts while you are splicing a hot wire and your plyers bang against the firewall welding then to the firewall. Disconnect the battary and no blown fuses. But I seldem if rarly ever disconnect the battart. I have put in 3 head units and a few amps and various other things and haven't touched the battary.

larrendeuce · Dec 14, 2007

I'm suprised no one said to prevent accidental starts.

gsjohnson · Dec 15, 2007

So the battery won't go dead while you work with the drivers door open

2000fordstanggt · Dec 15, 2007

gsjohnson said:
So the battery won't go dead while you work with the drivers door open

take the domelight bulb out

97speedster · Dec 16, 2007

blacknblue2002 said:
why do all of the instructions to just about every part installation tell you to disconnect the battery before starting???

For instance...why do you need to disconnect the battery when you're just swapping out your intake plenum or throttle body???

It clears all of the previous air intake reading so that with the new larger quantity of air coming in it doesn't make the computer think you are running rich or lean and cause hesitation problems. It is also recommended that you leave it disconnected for at least 15 minutes before you reconnect to ensure all old data is gone.

Why does everybody do this???

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