Code PO402 EGR problem detected-Mechanic tested system-no problem found. on 1997 Toyota Camry

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Engine light came on at 123,000 mi. and was intermittent for a few thousand more miles when it finally stayed on. Mechanic could find no problems. Smooth engine & transmission performance with very good mileage. Now have 192,000 mi and still going strong. I live in No. Arizona so don't have to take smog test. I want to give car to my daughter in Los Angeles & need to pass test. Any ideas?
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Have you thought about turning off trouble codes? Give it a try, and see if the code comes back on. Chances are, it's a false code and won't come back on. Have you replaced the EGR valve yet. Goodluck
trouble code had been turned off each time the check engine light came back on. With no problems found, we just left it on thereafter. At 192,000 the spark plug ignition wires harness was replaced due to wear and the engine light was off when I picked up the car. It stayed off for about 3 days with local short trips. Took a long trip & engine light came on during trip and stayed on. And NO, the EGR valve has not been replaced since the car was new.