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!

Yes. All monitors need to get set after erasing a code. Basically, you need to run through every possible engine load situation for the computer to say 'ok, we're good now.'

Part throttle cruise downhill, uphill, flat ground, WOT hot, cold, stop n go traffic, closed throttle coasting... 500 miles of highway alone won't cut it.

Thanks 70cuda383. That's what I was afraid of.

Being I was a Mopar tech for years but am retired now as stated it has to meet certain driving parameters before it will run and pass the test. The DRBIII tool we had at the Mopar dealer would give us a screen that showed what parameters needed to be met and would show when they were met when we drove it to the right parameters and the DRBIII would even show if the test was running. Are you sure there are no other codes or secondary indicators ? Course the catalast moniter has to have the up and down stream 02's working right to run the test. The PCM also uses the downstream 02 readings to help set the goal of the upstream 02. I used to be able to see if the upstream 02 goal was set in the DRBIII scanner as it may not run the test if the upstream 02 sensor goal is not set. I used to have the info on what was needed to make the test run as it has to have the eng on for so much time and be driven above a certain mph for so long and above a certain eng temp and so on. Sorry as I dont remember all the test parameters it needs to meet off the top of my head. Ron

As stated, the puter has a set of self tests it Hhas to run.most require a certain combination of throttle/speed/rpm etc. Some are even affected by outside temp.

I know evap monitor won't run if its too cold outside, but I don't think cat monitor is like that.

Are any other monitor not complete?

Is that the only monitor that is incomplete? The monitors run in a sequence and need to pass before the next one runs. If I were in your shoes I'd replace the upstream O2 sensor, they can be slow or biased lean/rich and not set a code and still cause issues. The ECM watches the O2 switching rate and the voltage and compares them. A fresh rear sensor will often flag a lazy old front sensor. Don't be surprised if you get a P0420 (Catalyst Failure) either way. Other than that the basics apply, clean oil, engine getting up to temp, NO exhaust leaks!, functional EGR, Good basic tune, Etc. If you really want to know just Google "OBDII drive cycle" It's not a secret, but it can be a PITA to run without a dyno programmed for it.

Wow, I agree that you might need an upstream O2 sensor too if the code hasn't cleared in 200 miles. It's too bad that those "driving requirements to reset computers" are kept so secret by the OEM's, but 200 miles sounds like a lot. I reset my Mustang's computer driving 10 miles, turn off/on & drive 5 more miles and it's OK (found this out by trial and error).

I don't want to jinx you, but my wife's Sebring had a code that just wouldn't clear and I had to replace the computer. I hope that's not the case for you. I had no choice since I had a deadline to get her license plates renewed with the emission test.

I don't know about Cali.but here in NY NJ your allowed 2 incomplete test up to 1999 a can still pass & 1 after 2000 & then I think after a certain year ? all have to be completed.

The monitors set in my 2000 Durango during a 25 mile trip that was 75% freeway.

Like 71GTX471 said, not sure how it is state by state, but here in WI you are allowed some unset readiness indicators based on year. I think WI is identical to what he said or close - I just had to nurse my dad's 99 Buick through with 2 I could not get to set. Some of the older cars it is a real bear to get them to set, and I believe emissions people have realized that hence the rule.

Thanks for all the replies, guys! I think I will go ahead and check into the upstream sensor after doing some more driving this weekend. The guy at the smog shop says he can't pass it with even one incomplete. Thanks again. I'll keep you posted!