Car wont start after tapping into power
 

Has anyone ever tapped into the power or ground wires for the AV Controller Unit? I have a 2009 g37s and I tapped into the yellow battery power wire and black ground wire (pins 19-20) to install some LED foot glow to a button. The circuit is complete because the led lights turn on but when I went to test it, my car wouldn’t turn off (engine was still on) and now the issue is my car won’t start (but car says it’s on). Does anyone know what this might be? Begging for answers and help so please let me know, thanks!!

So what does the engine START/STOP button do?

First thing I would do is disconnect whatever it is you installed and see if the car returns to normal operation. Then, if everything is good, you can look to other power circuits /sources.

Only question I have is why, with all the places you could have tapped for power & ground, why would you tap into a constant hot circuit? Least of all for the AV unit?

Also, first rule when working on electronics: DISCONNECT THE BATTERY FIRST! It is possible you blew a fuse somewhere...

yea I can give that a go but I just don’t see how that could affect my car the way it is right now but it’s worth a shot. And to answer your question, it’s because I only had a wiring diagram for the Av unit so I tapped into two sources that I knew for sure were power and ground. I didn’t think where I tapped in would matter. I also assumed that since the screen turns on when my car does that it wasn’t a constant . My second place was going to be the 12v cigarette lighter spot.

Pin 19 (yellow) is always hot. That is what provides main power to the headunit and also serves as a "memory retention" function. The AV system (and screen) only turn ON when the ACC or IGN relay(s) are energized (ie. when you start the car).

Being that you did the install with the battery still connected, anything is possible. One little touch to the wrong wire will knock half the car out... just see how many folks had issues installing radar detectors to their mirrors...

I would not use a constant power source for any accessory lighting. It takes one time for you to forget to turn the light off and you'll end up with a dead battery. But, your car...

I would check fuses 3, 4, and 19 in the driver side fuse block. Just to make sure... Does everything else seem to work?

i have checked the exterior fuses near the battery, haven’t checked interior. Hopefully it was a fuse. I do really appreciate the help by the way so thank you. Clearly there’s much to learn and I’ve already learned a lot from this project. I will undo the wiring I did as well as check the fuse boxes and let you know. The windows won’t go up, remote locks, power seats all won’t work but the exterior/ interior lighting was working and lights on the dash

There is always a learning curve and that is why forums like this one exist.

Definitely check the fuses in the driver side block first. Windows and locks, as well as your START/STOP, are all controlled by the BCM. One blown fuse is all it takes.

As much Frankensteining as I've done with the electrics in this car, I've come to find they are very solid overall. I'm sure you'll figure it out. Keep us updated...

The engine start/stop button is connected directly to the BCM (body control module).
When the button is pushed, the BCM sends a signal to the IPDM/ER (power distribution module by the battery) to turn on a few relays and start the engine.

Somehow the communication between the BCM and IPDM/ER has stopped. That's why you can't start the engine.
You should check every fuse with an ohm meter in all three fuse locations. Battery, IPDEM/ER and driver's kick panel.
|f you are lucky it is just a fuse...

Good luck!

Now that my battery is drained and the fact that my car won’t even turn on , will fuses have any power going through them? I’ve tried testing a few with test light probe but none of them seem to have any power. I’ve visually inspected a bunch such as the A/T CONT etc from the batteries fuse panel and I just checked the interior ones visually for a couple such as battery power ignition and start stop etc… no fuses are blown or split . How can I use an ohm reader or test probe to verify the fuses when my car wont send power to the fuses? Just let me know and I’ll give it a try. Thanks guys

Proper way to test a fuse is to pull it and use an ohm (Ω) tester. You don't check resistance on a live circuit.

If the fuse is good it should read 0Ω resistance. Bad fuse will be infinity (open circuit). It's unusual to get a value greater than 0 but not infinity. If you do, I'd consider that fuse bad too.

it is pointless to check fuses with a test light if your battery is drained down. you can use a dvom and it would show battery voltage across the fuse, be it 8v or 5v or whatever volts your battery is at. fuses that are powered on by the ignition sys will not show any voltage as you stated battery is drained down and it won't be possible for the ignition sys to energize anything.

Update
 

Great news today! Dealership got back to me and said they just had to clear some codes that were preventing the computer systems to work properly since I tapped into the constant battery power wire for the av controller unit. Irritating to know it was something so little yet out of my control but also relieving to know it wasn’t due to any direct mistakes I made or anything I could’ve checked and fixed myself.

just wondering whose "direct mistake" is it then with the issues that arose? the car didn't tap into the power wire to install some aftermarket device. nor were any repair shop tech hired to install anything. the wires didn't magically decide to short themselves out and create fault codes for the different computer systems. well i'm glad the car is repaired properly but you need to research what you are doing so stupid issues such as this don't arise again due to incompetence or nonqualification

hahahha buddy it was a safety precaution that the computer in the car does when tampered with. Where would I find that info prior to giving it an attempt? But thank you for your input :)

Did the dealer provide you a list of the codes they cleared, by chance?

Either way, glad you are up and running. Thanks for the update.