[Mark_AlbanyNY]

Hello

I had originally been dealing with a P0141 code which pointed to a bad downstream O2 sensor. Had it replaced this past Wednesday and all seemed well.

3 days later and I now have a P0420 code which looks like it points to the Cat Conv. ?? Anyway, my mechanic expressed some difficulty when he installed the O2 sensor -- needed a torch to get the thing out and something about needing to rethread it. Anyway could the recent installation of the O2 sensor have anything to do with the P0420 code I am now getting?

1998 Camry 4 cyl. 5SFE; 2,2L
157,000 miles.

-Mark

 

[fjaen]

Did they put on a denso o2 sensor? I've seen cheap o2 sensors do this a lot. The P0420 code comes on when the catalytic converter efficiency is less than either 90 or 95 percent... extremely annoying and narrow range. Sometimes with a cheap aftermarket sensor, the voltage generated by o2 sensor under normal operating conditions is some extremely small amount lower then what the original equipment (denso) sensor would put out, due to manufacturing variances and stuff.

Because of how anal our toyota computers are, even small discrepancies can make the computer think your cat is bad. the downstream o2 readings are compared AGAINST the upstream o2 sensor readings to measure cat efficiency... so the fact that they are different brands might play negatively into that comparison.

If it is the denso one, I would wait a month or two for the thing to wear in a bit... couldn't hurt. If at that point you still have the code, you might actually have a cat issue.

 

[93celicaconv]

I agree with Fjaen. If the mechanic put in a non-OEM downstream O2 sensor, that has led to this DTC many times.

I'm assuming a North American produced (rather than manufactured in Japan) with Federal emissions (rather than California emissions) [this all is significant when dealing with emissions DTCs on Camrys], you Camry's downstream O2 sensor part number from Toyota would be:

89465-33120 REAR (07/1996 - 12/1997) Denso P/N 234-4137
89465-06020 REAR (01/1998 - 07/1999) Denso P/N 234-4137

For some reason, the Toyota part numbers are different depending upon the date of manufacture, but the Denso part number cross reference is the same. Perhaps the length of wire on the O2 sensor was different, so Denso only supplies the longer wire at this time?