"O/D Off" light flashing: Problem Solved !!!
It was caused by a vacuum leak through a cracked rubber cap that was supposed to seal an unused vacuum port that hooked into the purge solenoid valve. Car has 107K miles so it's a no-brainer to look for defective rubber anything at that age.
Additional symptom was purge control solenoid valve clicking on and off so rapidly that several of us mistakenly thought it was engine intake/exhaust valve train noise.
I replaced the defective cap, zeroed out the error codes and did the high acceleration onto the freeway "on" ramp that had caused the "O/D Off" to begin flashing previously. No flashing "O/D OFF" light. Yeehah!
So then I removed the good cap and put the old cracked one back on. I did the high acceleration onto the freeway on ramp that had caused the "O/D Off" to begin flashing previously and , sure enough, it began flashing again.
Yeehah again!
Now that I could duplicate the failure, I removed the old cracked cap and installed the new cap. Zeroed out the error codes and no problem since.
If the trouble-free performance continues for a few more weeks, I will gradually regain confidence that the car is OK once again.
chris
p.s.> Before installing the new cap I boiled a coffee cup of water in the microwave and then soaked the new rubber cap in the hot water for a minute or two. That made it easy to install.
