Anyone good with OBD II code readers? 98 dodge van

[hosehead]

hey guys, a buddy of mine asked me to help him with his 98 dodge van with a 360. It has 110,000 miles. It needed a downstream oxygen sensor as the "check engine" light was on. I replaced it with a Bosch unit and reset the code reader. The check engine light then stayed off.
Now, everything is working properly but I cannot get the "catalyst monitor" code to reset. There are no pending codes and the guy at the smog check inspection station(I'm in kommiefornia) said sometimes you have to drive the car for hundreds of miles before it will reset. He claims this is a dodge thing.
He does own a garage also and said that there is nothing wrong with the computer or the engine. I just need to keep driving. I have driven this van for over 200 miles already. Anyone have any ideas on why this code won't reset? I have included a pic of the code reader. Thanks in advance!

 

[discharger1332]

with my 98 truck i had to drive at different speeds to get it to reset. if you do a google search the info is out there. from memory it needed to be over 60 for 10 or 20 miles then under 50 for some miles the over 60 again. I was in socal at the time so i had to do it at certain time of day to get to speed on the freeway, lol. good luck

 

[hosehead]

with my 98 truck i had to drive at different speeds to get it to reset. if you do a google search the info is out there. from memory it needed to be over 60 for 10 or 20 miles then under 50 for some miles the over 60 again. I was in socal at the time so i had to do it at certain time of day to get to speed on the freeway, lol. good luck

Thanks discharger! Since you have lived here, you know the challenges of driving how you want to. Lol. I've looked around on the internet but the info is all over the place. I will try your method for sure!