[bake]

Do I really need to disconnect the negative battery terminal to install / uninstall BMS Stage 1 tune?

[lsturbointeg]

Heres what I found from what Terry @ BMS posted
Thread:*N55 Stage2 Harness DIY

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(#3)*

Terry @ BMS*

Here are the N55 535 / F10 specific install directions.*

1) Disconnect the negative battery terminal.
2) Install the red, black, green, and brown wires in the DB25 AMP connector as shown above.
3) Remove the passenger side trim panel by lifting up the center of each of the press on plastic rivets and then lifting up the rivet itself.
4) Route the JB4 control box under the rubber weather stripping in to position as shown. If you are unable to reach the change around the sensor connector routing you've used as needed to ensure sufficient slack in the harness.
5) Connect the red power wire (+12v) to position A. The black plastic cap will pull straight up and you use a 10mm socket to loosen the bolt to attach the wire.
6) Connect the black ground wire to position B or any suitable ground location. We used a TORX screw that is just out of shot in the the photo below.*
7) Connecting the CAN wires is the most difficult part as you'll need to use the included removable wire taps. The brown wire (C in photo) connects to the yellow CAN wire as indicated. And the green wire (D in photo) connects to the black/blue wire right next to it. Both OEM wires will be twisted together in a pair so you will need to untwist them a bit to expose enough wire to make room to attach the taps. For those with the special posi-tap screw couplers see image below for directions on their use.
8) Once done reconnect battery.
9) Connect the BMS USB cable (which will normally sit under the black plastic cover) and connect to the JB4 interface. With engine running select "start logging" and you should see engine RPM start moving, etc. If you don't, then likely an install error has been made or the CAN wires do not have a solid connection. In that case disconnect battery and further troubleshoot.*
10) Ensure boost solenoid connector is installed for Stage2. Stage1 has this disconnected but it should be connected for Stage2. It's the connector with the blue wires.

Also note the F10 uses special N55 firmware so be sure to only upload firmware that has "F10" listed in it, or your vehicle will become a large paperweight until the correct firmware is uploaded.

[mike@x-ph.com]

Originally Posted by bake

Do I really need to disconnect the negative battery terminal to install / uninstall BMS Stage 1 tune?

Better safe than sorry


Yes disconnect it

[ATXF10M5]

I didn't. But this doesn't mean it's safe. Just figured since I'm not tapping into wires and just plugging/unplugging that I'd go for it. Of course, proceed at your own risk.

[bake]

Originally Posted by ATXSGF10

I didn't. But this doesn't mean it's safe. Just figured since I'm not tapping into wires and just plugging/unplugging that I'd go for it. Of course, proceed at your own risk.

Thanks, that is what I was thinking on the Stage 1. For a Stage 2, I understand where it would make sense looking at the installation instructions.

[Luky]

I didn't either and no issues. Only 2 plugs/sensors to connect for stage 1. Just make sure car is off and leave your key fob inside house so car does not sense you are near it and power itself up. (At least the e90 worked this way).

[jarockster]

I did not disconnect either and had 0 issues.

[Zer0Cool92]

Originally Posted by Luky

I didn't either and no issues. Only 2 plugs/sensors to connect for stage 1. Just make sure car is off and leave your key fob inside house so car does not sense you are near it and power itself up. (At least the e90 worked this way).

+1

I did the same, no issues