Headlights come on but the left on is dim. Bright
light mode the left side goes completely out. Also
my backup lights aren't coming on anymore.
It might be a wiring problem but most likely it's a bulb burning out soon, noting the high beam is already out. As a test, you can swap the bulbs from left to right but the smart thing to do is go to an auto parts store and purchase one #9007 bulb and ask if they would install it for you. If you upgrade to a better bulb, you should do both sides so they match. Buying in pairs is less expensive than one at a time. Ask them about backup lights. Both out at the same time might mean a fuse or wire, not likely both bulbs burned out at the same time. Being a police car, check for bullet holes too.
I've replaced both bulbs even brought the highest beam bulb there was and it's doing the same thing. Where exactly is the headlight grounded to the car do you know?
I'm big on checking voltage and ground circuits. Use a test light.
The top wires at headlamp is voltage, hi beam, lo beam, the bottom wire you can't see is black, that is chassic ground. You can use a test light to check for voltage. In the diagram, the single wire on the left side of lcm/lighting control module, should be hot with headlamps on hi beam. If not I'd have to check dimmer switch. if it is hot, the wire at the bottom on right side, lcm, in diagram, should be hot. If it is, maybe problem with Lcm? There is that wig/wag component at top right of diagram, that could kill hi beams. For testing hi beam, left side, you could leave a pigtail at both ends, clip the wire, run a new wire, the new wire bypasses the wig/wag, to the pigtails at lcm and left hi wire at head lamp, see if left hi beam now works. There are possible trouble codes for lighting system. Check for applicable trouble codes. Around here some of the national brand auto stores will test po codes for free. I can only help with testing.
I miss-spoke. If the hi beam circuit from lcm isn't hot. The wig/wag does have concerned.