PO420.....so now what?

[FunctionSpec]

Air/fuel ratio sensor(AFS B1 S1) voltage should be around 2.8V to 3.8V idling. Stoichiometry is at 3.3V. A voltage of 3.44V means a lean condition (A/f ratio sensor output is the opposite of what happens in a oxygen sensor).

I'm assuming it may be the catalytic converter because of your previous problem. Since you accidentally ran diesel and gas, it didn't burn completely when trying to drive the car which dumped a bunch of raw fuel onto the Cat causing it to overheat and slowly deteriorate. Also some diesel fuel was probably still in the system after draining it plus mixed with higher octane fuel(resists detonation) caused the engine to slowly dump unburned fuel onto the cats. Which is probably why it took awhile for a CEL to come on.

I would test out the O2 sensor(sensor 2) to check for proper operation since it is cheapest to replace and then replace the cat if all sensors check out correctly.

[Shroomster]

Originally Posted by FunctionSpec

Air/fuel ratio sensor(AFS B1 S1) voltage should be around 2.8V to 3.8V idling. Stoichiometry is at 3.3V. A voltage of 3.44V means a lean condition (A/f ratio sensor output is the opposite of what happens in a oxygen sensor).

hmmm guess I had the lean/rich backwards

[la_scanner]

Originally Posted by FunctionSpec

Air/fuel ratio sensor(AFS B1 S1) voltage should be around 2.8V to 3.8V idling. Stoichiometry is at 3.3V. A voltage of 3.44V means a lean condition (A/f ratio sensor output is the opposite of what happens in a oxygen sensor).

I'm assuming it may be the catalytic converter because of your previous problem. Since you accidentally ran diesel and gas, it didn't burn completely when trying to drive the car which dumped a bunch of raw fuel onto the Cat causing it to overheat and slowly deteriorate. Also some diesel fuel was probably still in the system after draining it plus mixed with higher octane fuel(resists detonation) caused the engine to slowly dump unburned fuel onto the cats. Which is probably why it took awhile for a CEL to come on.

I would test out the O2 sensor(sensor 2) to check for proper operation since it is cheapest to replace and then replace the cat if all sensors check out correctly.

1/30/09 - fucked up car
1/31/09 - "fixed car" to a a certain extent. LIGHT NOW ON!
2/10/09 - grandma worrying about light on. takes to toyota they say under $1,000
2/11/09 - grandma takes to route 66 tires and auto in glendora. was there for misc crap but he gave her his word spark plugs are fine. LIGHT OFF
3/14/09 - OH SHIT! LIGHT BACK ON! grandma furious and takes back to route 66 tires and auto in glendora.now he changes mind and says oh yeah, bad bad plugs. replaces them. $138.00. LIGHT OFF NOW
3/16/09 - LIGHT BACK ON!

in meantime im pondering and decide to but innova code reader. and here we are....