Hi I have code 43 and need to know how to fix it. I was gong to replace ecm but wanted to make sure because it's not cheap lol any info appreciated...

 

What we generally do is to erase the code and see if it comes back.
If it does that confirms a definite fault. If it does not come back sometimes poor quality fuel could cause the engine to not respond when the system runs its test.
I wouldn't consider replacing the ECM until all other tests pass and no fault is found.
A faulty knock sensor can fail and send false signals to the ECM, make sure the connections at the sensor are good.