Fog lights not working on a 98 Toyota avalon

I know the car has factory fog lights and when I replaced the switch to accommodate fog lights they won’t turn on but the bulbs are new and I am pretty sure the wiring is factory. What should I check for and what is the relay I should be using? Also if anybody has wiring diagrams available for the fog lamps or do you know where I can access them?

Look at the front of the car.

Do you see two extra lights other than the regular headlights?

If not, the vehicle doesn’t have fog lights.

Are you sure you don’t mean Daytime Running Lights?

Because the vehicle did come equipped with DRL’s.


Your local Toyota dealer’s parts guy will have wiring diagrams AND schematics (you’ll need both) for them. He also should have a procedure for installing the optional fog lamps. Ask nicely and they’re usually happy to print a copy for you.

You’re probably going to have to buy an additional Toyota wiring harness that will plug into an already-existing plug in a wiring harness behind your dash, as well as a Toyota relay. You’ll then need to find (using the wiring diagram) the fog light plug in the wiring harness under the front of the car. This will be two wires, one hot and the other ground (it doesn’t use the chassis ground at this point in the circuitry).

I can tell you from experience that the connectors, wiring harness, and relay are not cheap, but you will not find an aftermarket source. And I recommend you do it right or the fog lights won’t go off when you turn the key OFF, or go off when you turn the high beams on (lessening the total current draw). You could easily configure your own wiring, but I’d suggest doing it right.

For the record, I wanted to buy the connectors and build my own wiring harness. I have the technical knowledge, including IPC 610C and J-STD- 001 expertise, had the part numbers, and even have the pin-pushers to install the pins. I researched all the way down to Toyota’s connector part numbers… and when the parts guy looked them up the Toyota documents said Toyota would not sell the connectors separately. I tried going to the major connector manufacturer catalogs, but the part is Toyota proprietary and I could not match the connectors. In short, I had the connector part numbers, their interface drawings, and still could not get the connectors. I gave up and ordered the Toyota wiring harness.

Your Title to this situation is rather misleading… Basically your vehicle does NOT have Fog lights…and you are trying to basically install them. The factory usually wires the cars up using the same harness so that adding them shouldnt be difficult at all. What they may NOT provide from the get go is the fuses associated with that system…and or The RELAYS involved. Could be just one relay…2 max.

The owners manual should steer you to what the fuse value should be…and also where the relay plugs into the under hood fuse/relay box The same car in a salvage yard would basically answer all your questions on the spot… You can also go online to gather the same information…look at pictures and such…

What you are trying to accomplish is a pretty easy affair…just look for the info you need on the net. We wouldnt know these details off hand unless one of us had the same vehicle with Fogs to advise you thata way. But again…this will turn out to be an easy job to do if all the wires are there waiting for you…


As far as I was told the fog lights were there from the factory and the previous owner had been in an accident and left it with the body shop where we bought it. I was not able to really find anything online concerning the fog lights.

So you are asking why factory Fog Lights are not working? Just go under the hood or dash and ensure the fuse is good. Then find the Fog light relay under the hood and troubleshoot from there…the relay is what sits between the on/Off switch and the actual Fog Lamps… Its pretty simple to diagnose the system once you know the fuse is good and you are at the Relay under the hood…just carryout some troubleshooting steps from there.

The Relay under the hood will be set up like most other relays…This one will be a simple setup. Pull the relay and read the diagram that is written on the side of the Relay cover…Then just use a Volt meter or Test light to verify what the diagram on the relay shows you.

You can probably lookup a simply Fog lite relay diagram online as well… If you need more assistance I will send you a link to a basic relay diagram. But it is actually written on the side of the relay itself.


Stop by the dealer’s parts window and get a copy of the fog lamp wiring diagram and the schematic. He can even print the fog light installation procedure for you (they have them for the dealers to use). You can then track everything down and see what’s already there and what you need to purchase. Trust me, you’ll save yourself a lot of aggravation. I’ve done this before.

I finally found the right wiring diagram.

When you turn the switch to fog, the Body Control Module energizes the tail light relay. The contacts in the relay close and power is sent to the 10 amp tail light fuse. This fuse also supplies power to the fog light relay to energize it. the contacts in the relay close, and power is sent to the fog lights thru the 15 amp fog light fuse.

All these components are located in the under dash fuse/relay box.

First check and see if the tail lights work. If not, check the fuse/relay.

If the tail lights work, check the fog light fuse/relay.


@“the same mountainbike” @Tester I will try to get the wiring diagram from the dealer sometime this week . I checked all of the fuses and relays that should be for fog lights and know the tail lights are working but I will check the other things you mentioned when I get the car back after tie rod replacement and try from there. I also have someone who has a bit more car electrical knowledge helping me out so he might be able to help me check everything. Thanks.