Harbor Freight $7 minimal multimeter (volt-ohm meter, VOM): https://www.harborfreight.com/7-function-digital-multimeter-63759.html

You gotta use something like this to know if power is reaching the headlamp socket.

(If you're into expense and/or status, you can go high end and get a Fluke multimeter for $499.99. There are thousands of multimeter makes and models in between.)

If there's no power to the socket, then you'll need a wiring diagram to trace the wires back.

 

Okay I just checked for power at the sockets and both of the sockets have power so maybe do you think it's a ground issue in the plug? because the multimeter I used I had to use a ground to a piece of metal so all I can think of its maybe a ground issue in the actual socket do you think I need to cut them off and get new sockets? But I can confirm that the sockets have power but the light still won't come on I've checked everything multiple times.

 

I assume that your Avalon has halogen headlamps.

If you don't feel confident diagnosing this, an easy way out would be to bypass the existing wiring by adding a wiring harness like this one:
https://kensun.com/products/universal_single_beam_relay_wiring_harness

The harness is intended to add an aftermarket HID kit, but it will work in your case.

You would need two of them, one for the low beam circuit and one for the high beam circuit.
They are plug and play and very straightforward.

The harnesses would fit very cleanly and invisibly under the plastic covering that runs across the front of the engine bay, above the radiator, running from the driver's side to the passenger side.

You would plug each of the relay input wires into the existing working low beam and high beam connectors on the driver's side and plug the output 9005/9006 connectors directly into the halogen bulbs, and run the power wire(s) to the positive battery terminal, and the ground wire(s) fits very nicely under the bolt securing the bracket over the battery.


If you needed help installing this, I'd be happy to provide help online or over the phone.

 

If you can confirm that the positive side is getting voltage then you can either make your own ground or you can trace out the ground and find out why it is not grounding. Also keep in mind, when testing make sure the component you are testing is ON or OFF depending on what you are testing for. Can't test a light if the light is not on.

 

Yes I turned on the low beam socket and hi beam socket while they were turned on and I am getting a signal from the positive. Maybe the ground is messed up some how in the socket if thats possible? Someone told me just cut off the socket and install new ones. Easy and cheap. But my thing is I dont wanna buy new sockets and the issue is actual the ground connection... not the ground in the sockets.

 

The autozone headlight electrical diagram shows a single ground for both left and right headlights. https://www.autozone.com/repairguid...ring-Diagram-2001/Overall-Electrical-Wiring-Diagram-2001-1/_/P-0996b43f8037894d

You might have to scroll down to get to the headlights schematic.

Since one side is working, the ground from the junction connector is good. If I'm reading it right, the headlight switch gathers the power from both left and right, so that wire run is OK. (The circuit has power feeding from the fuse to the bulbs, then from the bulbs to the switch via a junction connector, and finally from the switch to a single ground in the instrument panel.

Looks as though you might have an open in the wire that runs from the headlight socket ground pin to the junction connector... unfortunately, this diagram doesn't tell you where that connector is.

Another option is a break in the ground wire at the headlight socket or near it. Or a totally goobered socket.

If you did get a multimeter, you can check continuity from the ground pin in the socket to chassis ground. The usual icon on the meter for continuity test is a combination of a fat-headed right arrow + vertical bar and a sound icon (dot with expanding "noise" curves to the right of the dot): https://learn.sparkfun.com/tutorials/how-to-use-a-multimeter/continuity

 

Edit: just went out to look at my 01. It looks as though headlight wiring snakes into the passenger fender. If the continuity test shows a bad ground from the socket (that is, no continuity from the ground pin to chassis ground (any available chunk of metal), it looks as though it would be easier to splice a new wire at the socket and run that to a (new) hole in a reachable place on the fender where you secure it with a sheetmetal screw such that the wire makes electrical contact. You might have to scrape paint away from around your new hole.

 

My bad - I've sent you to wrong wiring diagram if you have the driving lights (second set of lights inboard of what I'd call the outboard headlights.)

If you have the driving lights, they serve as the high beam. They also serve as the daytime driving lights, but routed through a resistor to drop the brightness.

I was going to send you to the diagram with running lights,but it's wrong. It still shows 2 dual-filament bulbs, right and left, rather than 4 bulbs.

That's the only way there could be JUST 2 wires to each bulb. These are single filament bulbs.


Sorry about this, I should have scrolled on down the Autozone diagrams and see their mistake...

And

 

FIXED

Turns out it was the plug that was messed up. I installed a new plug and BOOM back in business now both lights work.

 

FIXED

Well done!