Hey all - went to take my 09 Mazda 6 for a spin and it was dead from me leaving the interior light on. Anyway I jump the car and notice the check engine light is on. I shift into reverse and the car jerks like crazy but still able to drive in reverse. Now when I put it in drive the rpms go up a little but pressing the gas will not accelerate the car. Assuming that means it’s the trans and not the engine. Any thoughts?

 

Disconnect the battery, either fully recharge or replace the battery. Reconnect the battery, start the car, try reverse & drive & see what happens.

 

why? What issue do you think there is? How can the battery make these problems?

 

I've seen lots of problems caused by voltage fluctuations. The electronics are very voltage sensitive.

It doesn't hurt to try my advice, nor does it cost you anything. Nothing ventured, nothing gained.