Code P0420 and strange thing

[rfarkiya]

Hey guys

I have 2002 Toyota Camry with 123K miles on it. Few weeks ago P0420 came up and autorepair shop just cleared it thinking it might be bad fuel so he told me that if it comes again then we have to replace both Catalytic Converter and O2 sensor both. It didn't came back and i put almost 1000 miles on it.

The strange thing is that my mileage dropped to 15 to 20 MPG. I tried to do some diagnosis and found following after warming up for 2 minutes on 3000 RPM

Bank 1 Sensor 2 .012 to .820 fast move on low RPM and (steady at 3000 RPM)
Bank 1 Sensor 1 3.285 to 7.995V slow move

Does this mean that O2 sensor is bad? Sensor 1 is giving 3.28 to 7.995 volts?

Appreciate any help.

Thanks,
Prince

[njerald]

The voltage levels look fine but how does the waveform look?

Seems obvious that your shop does not follow a troubleshooting matrix but are parts replacers.

That's why there are Service manuals and Service procedures.

Do you have a Service Manual? Was P0420 the only code set?

Good Luck.

[rfarkiya]

Originally Posted by njerald

The voltage levels look fine but how does the waveform look?

Seems obvious that your shop does not follow a troubleshooting matrix but are parts replacers.

That's why there are Service manuals and Service procedures.

Do you have a Service Manual? Was P0420 the only code set?

Good Luck.

Yes P0420 was the only code he reset.