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Gremlins like this can be a pain to track down. You'll need a wiring diagram to tell you where the power to the dash lights begins and where they go to ground. Somewhere along that route there's a problematic component, connector or wire.

If you'd rather not go through the mind-bending process of tracking down electrical logic, you can throw parts at it, such as replacing the dimmer/rheostat. Rheostats (AKA poteniometer, variable resistor) that are intermittent or non-working can inject all sorts of interesting things into circuits.

According to the following listing, the part was used across a lot of models for many years (and I'm not recommending this seller, just depending on the parts applicability chart in his listing): 97-03 Toyota Camry Dimmer Switch Instrument Light Rheostat Control OEM 98 99 00 | eBay

 

OleAvalon,
I will take your advise and replace the dimmer switch it’s a cheap part so will will give it shot. I will post the result. Thanks !

 

OK. Just be aware that firing parts at a problem can add up and still not solve the issue. If you don't have one, you might want to get a factory service manual or a 2-day subscription to the online Toyota information service tech info, Toyota - New Subscription

The latter will give you the most comprehensive array of info plus a more efficient search mechanism. My 2002 FSM Part 1 & 2 (I don't have the electrical or transmission volumes) has a miserably bad index, making searches difficult. (2002 because it was the cheapest on eBay and it's a mathematical average between our 01 and our 03 Avalon.

The hell of it is that electrical gremlins almost have to be DIY when your car reaches a certain age/value, since diagnostics take hours to perform. Done by a shop, the cost goes up rapidly. Unfortunately, they require in-depth diagrams ($$) and manuals and repair write-ups, such as you get in the TIS subscription.

 

Or, putting on my ghetto fix hat, there are lots of cute little battery-driven LED string lights that, with a suitable lightblocking backing on each LED, could be strung along outside your instrument cluster (Toyota calls this the Combination Meter). Light block for you, with the other side shining through the clear plastic onto the dials.

20/50/100 LEDs Battery Operated Mini LED Copper Wire String Fairy Lights 10M | eBay

 

Gotcha, I found a dimmer switch on eBay for $14. Fingers crossed that’s the fix. Thanks,