maxpower wrote:

> "George Chandler" > wrote in message
> ...
>
>> Our 2002 Dodge Grand Caravan is due for NJ State Inspection this
>>month, and in keeping with Murphy's legacy, our "check engine" light
>>decided to appear a week ago. Using the key on-off sequence, the
>>failure code was a P0456, or small evaporative emissions control system
>>leak. Researching the situation, I found reports about this occurring
>>via a loose fitting or failed gas cap. We have been wanting a locking
>>gas cap anyway, so I replaced same, but neither the "check engine" nor
>>the P0456 failure code disappeared after several engine cycles. Not
>>knowing at this point as to whether the problem had been solved or
>>whether the PCM was taking its time resetting, I purchased an Actron
>>9135 scan tool and reset the P0456 failure code.
>>
>> After resetting the code, four of the I/M parameters went to "NOT
>>READY" (CATALYST, EVAP SYS, O2 SENSOR, and HO2 SENSOR). After 50+ miles
>>of driving with several engine cold-hot cycles, the "check engine light
>>has not reappeared, and three of the above I/M parameters have gone back
>>to "READY", but the HO2 SENSOR parameter remains at "NOT READY".
>>
>> Does anyone have any info as to how long this HO2 SENSOR code will
>>take to reset? I have the factory service manual, but can't find any
>>info there. If its going to take 30 or 40 engine cycles to reset, I'll
>>have to just let the car fail inspection, but would rather not go that
>>route if there is anything I can do to get this parameter back in line.
>>
>> Thanks in advance for any help!
>>
>>
>>George
>
>
> George, That's why you don't do a battery disconnect or reset the check
> engine lite with a scan tool because it will clear all the monitors that
> have passed. Each monitor has its own procedures to pass, some actually have
> to be driven at a certain speed under a certain load such as the EGR valve
> which is one of the hardest monitor to run. I normally advise the cust to
> drive it 2 weeks before they bring it back in for a test. It could take more
> then 40 cycles or less then 5. It all depends on if the engine is driven as
> the PCM monitor is looking for.
>
> More then likely you have a cracked hose under the vehicle next to the
> canister or a cracked hose behind the air cleaner housing.
>
> Glenn Beasley
> Chrysler Tech
>
>

Glenn,

Thanks for your reply to my question!

After I replaced the gas cap, I found myself in a predicament in
that I didn't know if or how long it would take the PCM to reset the
"check engine" light, or if I had even fixed the problem. The factory
service manual didn't provide any quantitative information in that area
(or if it did, I missed it).

Is the OBD-II arena such a "black art" in that there are no
quantitative definitions as to how each I/M is defined/reset? How do
Dodge/Chrysler dealers handle this type of situation on a service call -
can the DBM-II/III individually test/reset the failure codes and I/M
parameters?

Thank you again for your help!

George