There are big differences in the headlight wiring systems between a Camry with daytime running lights and one without DRL. With that said I need to know if your Camry has the DRL feature. If you are unsure look in the underhood fuse box and see if there are several relays and fuses installed that are marked as being DRL related.

I need you to confirm which part of the headlight system is inoperative?  The low beams, high beams and flash to pass feature.

Can you provide the part number of the relay you installed?

Location of where it was installed?

Did the old one appear to have any heat damage?

Do you still have the old one?

It sounds like the headlights only worked with the dimmer switch in the flash to pass position and that only worked for an hour or so.

I have attached a wiring diagram and would suggest you start by testing for power on the LH & RH headlight fuses with the headlights switched on.  If there is power on those fuses then move on to checking the bulbs themselves.

If there is no power on those fuses then listen/feel to see if the headlight relay clicks when the headlights are switched on. If there is no click then check the 40 amp main fuse.

Let me know what you have to test with?

Ohm testing a fuse is okay to tell if the fuse is good or not but will not help to diagnose the system. Testing voltage is what needs to be done. In one of your earlier replies you stated you were testing voltage but were getting a reading of 22.2 volts. Either that was a typo or the meter is not set up correctly. Can you upload a picture of your meter so I can help make sure it is set up properly for testing?

To test DC volts you will need to rotate the meter switch to V/Hz and then use the Mode button to make sure you are reading DC volts. It should either display “DC” or two horizontal, parallel lines with the top line being solid and the lower line in dashes. To confirm the meter is set correctly touch the red lead to the battery positive terminal and the black lead to the battery negative terminal. With the engine off you should expect to see a reading of 12.6 to 13 volts.

After confirming the meter is set up and reading correctly continue with testing at the LH and RH headlight fuses with the headlight switch turned on.

Yes, black lead to battery negative and red lead to the fuse terminals. Headlight switched on, there should be a nominal 12 volt. You should have a very similar reading at the fuses as you did to the battery positive terminal.

If it is reading 5 volts then you will need to remove the headlight relay and check for 12 volts at terminals 1 & 4.

Can you send me a picture of the terminals on your relay and the mating connector in the fuse box? Is there a diagram on the side of the relay case? If so send and image of that too. You will need to do a quick reply for each picture. Only one image is allowed per reply.

Between your testing descriptions and the wiring diagrams I would say that the problem is either going to be in the headlights switch itself or in what is called the integration relay. The integration relay is more of a basic body control module than an actual relay.

Does the headlight switch feel like is has distinct clicks when operated in the various positions? Headlights on and off, dimmer high, low and flash to pass.

The integration relay appears to be powered by three different fuses.  Dome, Gauge and Door. You might want to check and see if those fuses are good and properly powered. The Dome and Door fuses are battery powered at all times. The Gauge fuse is ignition powered.

Testing beyond that is going to require removing panels under the dash and around the steering column. Are you comfortable going forward if needed?

The integration relay is a module that is attached to the backside of the interior fuse box.

Link to integration relay. 

I need you to do one of the following to check and see if the low beams will work. Remove the cover from one of the headlight relays and then place it in the fuse box. Turn the headlight switch on and see if the contact arm closes. If it does not use your finger and push the contact arm in and note whether the low beam headlights work or not or…… make up a jumper wire and jump between the two larger terminals in the fuse box and note if the low beams come on or not. Also see my previous post for a link to an integration relay listed on Ebay. I had included a link so you would have an image of what it looks like.

You mentioned the lighter fuse but have you checked the three fuses that I recommended checking earlier to make sure that they were good and properly powered. If so you should feel the relays and the integration relay module to see where the clicking is coming from.

With the jumper wire installed does the dimmer switch control high and low beam operations?

According to the wiring diagrams that is how it should work. Low beam stay on at all times with the headlights turned on and the high beams come on in addition to the low beams when commanded. Knowing that tells us the the headlight/dimmer switch has a functional ground attached to it . The next step will be to test the headlight dimmer switch to see if it is functioning properly.

You will need to test the red/yellow wire at terminal position #13 at the headlight switch connector. The headlight switch sends out a switched ground signal when the headlights are turned on. So you need to connect the red lead from your meter to a known power source and the black lead of your meter to the red/yellow wire at the headlight switch harness connector. The meter should read nearly zero volts with the headlights turned off and nominal battery voltage when the headlights are turned on.

You can also connect a known good ground to the red/yellow wire at the headlight switch connector and see if you can turn the headlights on and off. If you can the headlight switch is faulty. If you cannot, chances are that the integration relay/module is faulty.

I would skip that test then. Instead I would go to the interior fuse box and locate the integration relay. I cannot find a breakdown of the interior fuse box but the integration relay/module should be located at the lower rear of the fuse box. I think there will be a connector along the lower edge where you can find the same red/yellow wire at position #4. There should also be a red/black or maybe a red/blue wire at position  #3. You may be able to follow the harness from the headlight switch down to where it connects to the fuse box.

It is called an integration relay but looks more like a module. I attached a link 6 days ago for your reference. It is a part being offered on eBay. You can also search for a used integration relay and or interior fuse box for your 2000 Camry to see what it looks like and where it is installed in the fuse box.

I cannot overstate enough. Do not randomly attach a ground wire to other circuits than the ones I outline. You can cause damage to components and at bare minimum blow fuses.

With that said, when you grounded the red/black wire and the high beams came on that told us a lot (the wiring between the integration relay and the headlight relay is okay). I am assuming that the headlight/dimmer switch was connected at this point of testing and that the dimmer switch was in the high beam position. Is that correct? If that is correct, attach the ground wire again to the red/black wire and work the dimmer switch to confirm you can switch between high and low beams.

If that test goes okay then I would recommend replacing the integration relay/module.  You must make sure that the Dome, Door and Gauge fuses are good and properly powered. The Dome and Door fuses should have power at all times and the Gauge fuse should be powered with the ignition switch on.

Also we need to check the ground wire going to the integration relay/module. It is a white/black wire. It is supposed to be in position #10 of the I17 connector. If your dome lights and door locks are working properly it is likely okay.

Lastly I want to confirm that you are referencing the wiring diagram that I attached early in this conversation? Doing so should help give you an understanding of how the system works.

I would recommend replacing the integration relay/module. You most likely will have to buy a used part. From what I saw new ones are no longer available from the dealer. I would check with one or two  dealers first though. They may be able to give you part numbers that will help you locate a part if they cannot supply one.

No problem. Make sure you let me know when it is all fixed up.