My brother have a check engine light on his 1997 Toyota Tacoma, 2.4L 5sp.
After taking it to Advance Auto part he got print out with the following:
PO420

Catalyst efficiency below threshold (bank one)

Any one has an idea?

Thanks.

My Stepson's 2000 Taco just threw the same code yesterday. According to the service manual, the most likely cause is a bad O2 sensor in front of the converter. I checked his out with and ohm meter, and sure enough, the sensor read way out of tolerance. The stealer quoted him about $120.00, I think -- said they'd have to order it. I checked AutoZone and NAPA online, and both were more expensive. Good luck.

Thanks for information, I'll pass this info to my brother.

The best prices I found for our O2 sensors is urdusa.com . ~$85 for the Denso brand. I think I got the link off of this board at one time or another. But before I dropped that kind of cash for new sensors, how old are his spark plugs? A misfire will send raw fuel down the line to the cat. If you send more than the cat can take care of you'll end up with the P0420 code. My wife's 01 Odyssey threw that code off and on for a couple of weeks. I finally broke down and replaced the 95k miles original plugs (the plugs are platinum so they should last about that long) and not only does it run better (peppier) but she hasn't been greeted with the CE light since then.

My truck, a 97, threw the same code, so I took it to autozone and they told me the same thing you said. But after seeing the prices for replacing the sensor I decided to take it to my local stealer to have them read it (only $30) I figured if the part was going to cost that much, might as well spend a little more to be sure. Not to mention mine would only throw the code every now and then. Like ever couple weeks and if the sensor was bad, then it should throw it right away.At anyrate, the dealer told me that my two o2 sensors were mimecing one another, and that ment my catalytic converter was going bad. Which was even more costly to repair. So I haven't fixed mine yet, the light comes one once ever 2 or 3 weeks. I figure it can't be completely bad yet since I drive it everyday. Just thought I'd give you my .02.

Chris

I'd tune your puppy up too. It couldn't hurt!

Thanks aging guys for your replies.
The truck had new plugs, distributor cap/rotor for about 10K
The light is always on, if computer is reset it goes off but comes back in about 20 min.

If you've replaced the plugs (with decent ones), then it's the o2 sensor... <img src="/forums/images/graemlins/cheers.gif" alt="" />

Just wanted to send an update that my wife's code came back. From further Net research it looks like a new Cat is in her future followed by at least a new front O2 sensor in case that was the guilty party that killed the kitty.