[n54cutz]

I finished my engine swap and tried to start the car and battery was dead, charged battery and nothing jumped it, started but was running like caca, finally got fed up with jumping the car so jumped it one final time started up then died, so I went to Walmart picked up a battery couldn’t find the marking on the old battery which ah rating it was so I just threw in a new battery(it’s some weird old battery I have never seen this company in my life also made in Korea if that helps) put in new battery went to start the car annnddddd anti theft now the car doesn’t start doesn’t do anything but the key still locks and unlocks the car and Ignition works but nothing, cant even connect to the car with MHD what do I do?

[Bims328i]

You need the correct battery. Can't just throw any weird old battery in it.

Use a scanner to see what is currently coded e.g. 90AH AGM and get the matching battery and correct size (could very well be group H8)

If the battery is otw out or improper size you can run into all sorts of weird electrical gremlins.

When doing the bat swap, disconnect and let it sit for 15-30 mins before proceeding.

[n54cutz]

I picked up a h7 I think the old battery was the one I took out I think it might be the tilt or sensor I have it jack stands and I’m also getting the roll back icon when trying to start it

[lookalikehuuh]

Originally Posted by Bims328i

You need the correct battery. Can't just throw any weird old battery in it.

Use a scanner to see what is currently coded e.g. 90AH AGM and get the matching battery and correct size (could very well be group H8)

If the battery is otw out or improper size you can run into all sorts of weird electrical gremlins.

When doing the bat swap, disconnect and let it sit for 15-30 mins before proceeding.

Nah an incorrect battery size/type won't prevent the engine from starting... it might not last longterm due to over/under charging but it won't prevent the car from starting at all. You can literally start the car with a jumper pack and no battery at all if your jumper pack is powerful enough. By weird old battery he probably means its a battery with not a lot of information on it like many do. For the record an E9x car can literally have H6, H7, H8 and probably other size batteries from factory depending on options. But even a fully loaded car can start just fine with a small H6 battery.

Anyway, can you put a picture of the "roll back" icon you get when trying to start the car? It could be the car is missing a safety measure when trying to start like the transmission is detecting its in drive or something (assuming its an automatic).