Last week my check engine light came on, just after my warranty expired, had it checked out it was code PO420 saying it was the catalytic converter... errrr cost to buy a new cat $1200, plus installation. OK, well I don't have that kind of money right now, but he said it was ok to drive for now. A few days later while I was getting up on the highway, the car made a whine sound and the check engine light went off, had it checked again the code was also gone. So the next day, the light came back on... errrr So then I had to fill up with gas, I used my usual Shell gas and as soon as I started the car, the light went off, and has not come back on. I am wondering if it was the cheap Citgo gas I've used the last 2 tanks. Like I said, I usually use Shell, but the Citgo station was so cheap, $2.97 compaired with the average of $3.11. Also my last 2 tanks had the worst MPG's I've gotten in a long time, 42.8 & 44.6, previous tanks in the summer are usually high 40's to low 50's. So could the error code have been a result of bad gas??? I was told the code could also mean a misfire, bad O2 sensor or the cat itself. So what are your thoughts?
I think that the only way to know for sure is to have the exhaust gas analyzed (i.e. have a tailpipe test like they do for a smog test). The P0420 code is a failure of the catalyst efficiency test. This test looks for oxygen storage capability of the catalyst by comparing the switching rate of the A/F sensor before the cat to the O2 sensor after the cat. So, if they do the tailpipe test, and the emissions are normal, then maybe bad gas. If the emissions are high, then you probably need a new catalytic converter.
<div class='quotetop'>QUOTE(dogfriend @ Aug 6 2007, 10:05 AM) [snapback]491229[/snapback]</div> And, if it IS a bad cat, then that's probably covered under the emissions warranty, which is longer than the normal warranty and would likely be free.
<div class='quotetop'>QUOTE(dogfriend @ Aug 6 2007, 11:05 AM) [snapback]491229[/snapback]</div> That's a good idea, don't know if it'd work here in CT. Because the engine won't run for the entire 2 min test, it's an automatic failure and won't display the levels on the standard tailpipe test. They test hybrids with the vehicle's On-Board Diagnostics(OBD) computer system, and since it was throwing a code, it'd fail that one too. And after 78 miles on the Shell tank, the light came back on. Someone else told me to have the valve timing adjusted....
<div class='quotetop'>QUOTE(babsrocks @ Aug 6 2007, 12:04 PM) [snapback]491268[/snapback]</div> My gas milage took a nose dive this year. I was using Stewarts gas. My milage was down a good 10 to 12 mpg. I switched to Citgo gas and put in some engine cleaner and filled up. My milage went back up within 2 tanks. Haven't had a problem sense then. gl
<div class='quotetop'>QUOTE(babsrocks @ Aug 6 2007, 09:04 AM) [snapback]491268[/snapback]</div> They could place the car in "inspection" mode to make the engine run continously. The dealer would be able to do this. They might have to compare a "normal" Prius to your Prius to determine if the catalyst is degraded or not. The light may be going out after a certain number of driving cycles without detecting the problem. I believe that the P0420 code is set after two successive driving cycles where the problem is detected.
<div class='quotetop'>QUOTE(dogfriend @ Aug 6 2007, 01:07 PM) [snapback]491326[/snapback]</div> Thank you dogfriend. I'll have it checked out again and see if they can do the test.
