1996 Camry - OBDII code P0420

Our 1996 Camry 4 cyl wagon has 165,000 miles and has not burned any oil. We get a check engine light sometimes and each time the code reads PO420 - "Catalyst System Efficiency Below Threshold-Bank 1". Funny thing is that it does not come on in winter months. Also, it only appears after driving some distance, say 50 -100 miles, then stopping at a stop light, upon pulling away from the stoplight the light comes ON. After reading some postings, I interpret this code as a degradation of the signal difference of the two oxygen sensors. In other words, there is little difference in the signal before and after the catalytic converter as measured by the oxygen sensors. Carbon monoxide coming out of the engine should be converted in the nickel catalytic converter, so the carbon monoxide reading should be lower in the post converter oxygen sensor. This could mean a bad sensor or bad catalytic converter, or possibly both. The question is: How does one decide on which is responsible? My thought is that if the catalytic converter is bad, then it would read bad every time you start the engine, unless it is not totally bad yet. Also, if a sensor is going bad it may not breakdown until some driving, after which is is really hot for some time period. Then again, if the sensor is totally shot it should real bad all the time too. Any thoughts appreciated on a line of attack. I have 1 year before emissions retesting. Thanks, HW

Reply to
hweems
Loading thread data ...

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.