Can someone please answer my question? I replaced a crankshaft position sensor on my son's 99" Dakota 3.9l w/5 speed manual trans. The truck was running rough & barely would would idle, it showed a DTC of P1391. I had the battery disconnected for a few days before I installed the new CPS (got the wrong part the first time and had to wait till the weekend to finish the job). After the sensor was installed & the battery reconnected the truck started right up and ran great and the DTC went away. The trouble now is that when I hook my code reader up it shows one of the I/M readiness monitors (the O2 heater sensor) has not reset it's self to ready status. Immediately after test driving I noticed that three of four monitors reset within 15 minutes of city driving. It has been almost a month and we have driven more than 700 miles, 4 tanks of gas, and well over 60 cold starts. We have even tried following the "Chrysler Drive Cycle proceedure for O2 Sensor Heater Monitor Drive Trace" but still this monitor is not ready. Is this a problem or will the monitor just set to ready on its own after time?
Thanks in advance, Mike

 

my old saturn did the same thing and caused me to fail a smog check. i drove it for like 500 miles after resetting the computer and it still hadnt registered. i hooked up my code reader and told it to erase the codes again even though there weren't any. then i pulled my battery and unplugged and reconnected my 02 sensors. popped the battery in after the computer had reset itself and drove it for like 20 minutes. im not sure which one of those things fixed it but it did and i passed smog the next day. the readiness monitor should be able to reset itself after one good drive and if it doesn't something is wrong

 

Hello kurbycar32!! My son just returned home from school last Saturday. I asked him how the truck was running? He said that it was running just great. I decided to hook my code reader up just to see if the O2 Sensor Heater Monitor was still running its test. To my suprise/delight it had finished running its test and had set its self to ready status.I guess that after nearly a month of driving the monitor finely decided to reset, anyway all is fine. Thanks for your reponse to my query, I appreicate it. Thanks again and have a Merry Christmas.