My car passes the emission part of the smog test.
Recently, the front O2 sensor was replaced.
Should I change the rear 02 sensor?

Any good smog mechanics in San Diego?
Thanks

get cat really hot then let idle for 20 minutes that should let it test catalist
seconday air is the hard one. start cold engine run at 1400 rpm for 7 minutes after eng tem has past 70 deg then let idle for 6 seconds then turn ignition off for 10 seconds then repeat
after the 7 minute high rpm when you return to idle you should hear the pump turn on
good luck

I ran it for 1400 rpm for 7 minutes after engine temp reached 70, then returned to idle. The pump turned on for a few seconds and then stopped.
I then repeated the 1400 rpm, returned to idle but this time it didn't turn on.

The next day I did the same thing, the pump turned on the first time but not the second time.

Is it necessary for the pump to turn on the second time I run at 1400 rpm, and return to idle?