OK,
I had the check engine light come on in my 02 with 20k miles. The Camry is under warranty, so I took her to the dealer. The diagnostic showed two parts bad (MAF and AF sensors). They replaced one and had to order the other one. But here's the odd thing:
When they replaced the MAF (Mass Air Flow) sensor, they told me the other one was on order but when I drove away, ***the check engine light was out and never came back on***.
About 10 days later, the part came in and I returned to the dealer to have the second sensor installed. When I looked at the ticket after getting the car back, it said "confirmed code (something or other) air flow sensor with diagnostic tool. Replaced AF sensor. Checked again with diagnostic tool and error code cleared."
OK. But if that AF sensor was indeed "bad"--why wasn't the "check engine" light on during the 10 days I was waiting for the part? In other words, if the diag tool can confirm that it was bad, why wasn't the check engine light on?
The scary thing is that I'm afraid that they somehow disabled the check engine light while waiting for the part--then never turned it back on. Could that be the case?