princess19

2005 ES330, 173K miles continually pulling a PS0420 code. MPG's between 18-22 and runs rich in a.m.. You can smell the exhaust and idle is around 1 to 1.5 RPM's. temp gauge is middle of C and H. I have had the car for 4 months. 3rd day after purchase CEL came on and seller cleared the code and denied any knowledge of it coming on when they drove it....yeah right!

Any ideas on O2 or Cat?

Thanks

hzt30

You need to check the efficiency of the cats by monitoring your downstream O2 sensor's activity. If sensor shows a lot of switching then cats are suspect. Downstream O2 should stay fairly steady.

Oro

What he's getting at is discussed in a technical, but not overly confusing, way here:

http://www.easterncatalytic.com/educ...he-po42o-code/

A few thoughts:

a) if your mechanic shop read that code and suggested that route, you need a better (either more knowledgeable or honest) mechanic for the next step. That's not an acceptable way to go at all.

b) If the problem appeared four days after purchase, you need to look into Texas' lemon law and see what recourse you have since the condition was there when sold.

c) your poor mileage indicates too much fuel (too rich) and it could be a combination of sensors that need cleaning and/or replacing.

Wht95scort

What he said. Any good shop should be able to diagnosis this issue for you and tell you what your problem is. I can also tell you an exhaust leak before the O2 can cause this code so have the shop perform a smoke test on the exhaust.

It's also safe to say your O2 sensor is working as its detecting too much oxygen so your problem is either the cat or leaking exhaust.

princess19

Thank you :-)

princess19

Thank you so much :-)thank you for all of your suggestions I will definitely follow them. Thank you for also adding the lemon law information I experienced that with a car dealership that was used about 15 years ago and ended up suing them over it. That's not really the route I want to take that again I believe the problem was pre existing and that they knew it when they sold me the car. So thanks again :-)

princess19

Thank you :-)

princess19

thank you for all of your suggestions I will definitely follow them. Thank you for also adding the lemon law information I experienced that with a car dealership that was used about 15 years ago and ended up suing them over it. That's not really the route I want to take that again I believe the problem was pre existing and that they knew it when they sold me the car. So thanks again :-)