Turn Signal/Parking Light Electrical Problem

I have a 99 jeep cherokee. Just recently, I noticed the turn signal on the passenger rear wasn't working the way it should. If I turn the right side on it would work fine until I turn the parking lights on. Soon as those are on, both lights blink one after another just like the front turn signals blink together.

Couple things I've tried..

Installed a new ECU I had laying around.

Ran a wire straight from the turn signal wire at the column to the bulb in the back(cutting the rear wire in half), and ran a wire from the parking light straight to the battery to bypass any wiring under the carpet.

Changed all the bulbs



Not sure what would cause something like this, especially since i rigged the wires so that both positives were being bypassed(I left the ground connected-maybe that's the problem?)

Any ideas??

edit: oh and another thing: my check engine light came on and is giving me a code about the neutral safety switch or transmission circuit switch or something like that. Could that have anything to do?

I should also add that the driver's side is a lot brighter, while the passenger side is a lot dimmer especially when both lights start blinking together.

I also had a couple issues with the dome lights blinking with the turn signals but I think I took care of that somehow.

OK...I guess I coulda searched some, but it turns out its the ground from that side of the wire harness.. i hooked a wire straight the the ground on the battery and now it works. not really sure where that ground runs too, but maybe ill search or just make a new one.

IIRC there is a common ground wire behind the panel on the drivers side where the spare tire is mounted that is for the rear lights.