OBD2 Yellow light

[jcaxico]

I have a 2000 Camry LE 4 cyl. with 176,000 miles.
About 2 months ago, the Check Engine Light came on.
I checked the Diagnostic Trouble Code and it had something to do with the EGR system.
The EGR checked out ok, so I replaced the EGR vacuum modulator and the CEL went away.
The only problem now is that when I connect my OBD2 code reader it gives me a Yellow LED light
indicating there is a possible problem. There is also a "CAT" monitor icon blinking.
I had to renew my plates so I took it to get it smogged and everything passed except for
Malfunction Indicator Light "This vehicle failed the MIL/Check Engine Light due to failure to successfully
complete all OBD tests." The tech told me to drive the car some more until I get a CEL.
I have driven this car for about 2 weeks now hoping that the CEL will
come on with some kind of DTC but it seems to be stuck on stupid and keeps doing the same thing,
No CEL, Yellow LED light on with "CAT" monitor icon blinking and no trouble codes.
Have any ideas?
Thanks
Update.
I drove the car on the street, no freeway, for about six miles and I got a green light thus completing the 2nd "Trip" for the "Cat" monitor.
No more blinking "Cat" monitor icon. Apparently, I was doing freeway driving only.