2000 Camry P0420 Code Novice

[starfleet]

Hi, I originally posted this over at the other Camry forum but got no help or even any relies. Hoping someone here might be able to offer some assistance.

I recently bought a 2000 Camry, 2.2 L California emissions, 5 speed manual with 72,000 miles. Shortly after I bought the car, the CEL came on. I bought an Autoenginuity ST06 scanner, and pulled the codes showing problems with the S1B1 wideband AF sensor heater circuit. Bought a new Bosch wideband sensor and installed. Cleared the codes. Fine for a day and CEL comes on again. Shows code P0420 catalytic convertor.

In doing research, I realize there are a number of factors that can influence this code. So I scan and record while driving. B1S1 voltage shows a pretty classic waveform pattern within normal range. B1S2 (post cat) voltage fluctuates wildly to the inverse of B1S1. Essentially, when S1 spikes up, S2 voltage drops to 0 or near 0. Not the pattern I expected.

Maybe related and maybe not, when driving at a stable speed and RPM around 2000, engine timing advance would go into the red zone. Not during acceleration, but when cruising. I have no clue as to what causes this or how to correct.

I have an Excel chart showing the relationship of the S1 and S2 voltage changes over a period of time if anyone is interested.

Any suggestions?

Thanks!

[JohnGD]

Read the following P0420 article:
http://www.motor.com/magazine/pdfs/012009_02.pdf

I think you may need to change out the downstream sensor as well. Use a Bosch universal planar type for your model/year that's more resistant to contamination than the Denso thimble you're going to pull out.

In addition, you need t make sure the engine is well tuned. Has the timing belt been changed yet? Valve clearances checked? etc etc.

Originally Posted by starfleet

Hi, I originally posted this over at the other Camry forum but got no help or even any relies. Hoping someone here might be able to offer some assistance.

I recently bought a 2000 Camry, 2.2 L California emissions, 5 speed manual with 72,000 miles. Shortly after I bought the car, the CEL came on. I bought an Autoenginuity ST06 scanner, and pulled the codes showing problems with the S1B1 wideband AF sensor heater circuit. Bought a new Bosch wideband sensor and installed. Cleared the codes. Fine for a day and CEL comes on again. Shows code P0420 catalytic convertor.

In doing research, I realize there are a number of factors that can influence this code. So I scan and record while driving. B1S1 voltage shows a pretty classic waveform pattern within normal range. B1S2 (post cat) voltage fluctuates wildly to the inverse of B1S1. Essentially, when S1 spikes up, S2 voltage drops to 0 or near 0. Not the pattern I expected.

Maybe related and maybe not, when driving at a stable speed and RPM around 2000, engine timing advance would go into the red zone. Not during acceleration, but when cruising. I have no clue as to what causes this or how to correct.

I have an Excel chart showing the relationship of the S1 and S2 voltage changes over a period of time if anyone is interested.

Any suggestions?

Thanks!

[starfleet]

John, thanks for the reply. I changed the spark plugs and the timing belt was changed only about 3000 miles ago. And I was thinking the same thing about the downstream sensor. Thanks for the suggestion.

Just as an FYI, what influences timing advance?

[Gibson99]

mass air flow meter (or map sensor, i can't remember which the 5sfe has), intake air temp, knock sensors (which your 4cyl may or may not have), cam and crank position sensors, and coolant temp sensor. oxygen sensor data doesn't normally affect ignition timing, only mixture. oh, and throttle position also has an effect.

that said, it's quite normal for ignition advance to be in the 20-30 degrees range under light load at cruising speed. it helps with emissions and fuel economy. as long as it's not pinging/knocking, don't sweat it.