Everybody,
Going by this freeze frame data, do you think it is the upstream O2 sensor, downstream O2 sensor, or the cat needs replaced. The car has 190K miles & has high oil consumption. The cat temps are only a few hundred degrees apart. I think they are supposed to be more....

Chris

 

The A/F and O2 sensors generate a voltage based on exhaust gas condition. If the car didn't have a cat, the sensors voltages in response to throttle action would kind of parallel each other.

The cats job is to convert the gas going into the to something that has reduced emissions. This reduced emissions results in a O2 sensor now having a different voltage output which is flat.

You need to compare the voltage of the A/F sensor ahead of the cat, with the O2 sensor voltage action of sensor after the cat.

For a working cat, the A/F sensor voltage will vary, while the O2 sensor voltage action will be nil. If the O2 sensor voltage is pacing the A/F sensor voltage, the cat is not working.

The internet has videos on this diagnostic.

Find the application in the reader the either outputs a real time sensor voltage as a number or as graph. Then compare the two sensors output as a response to throttle movement. For a working cat, the A/F voltage should be active in response and the 02 sensor limited.

 

thanks for the info...i will look at the live data portion to find those readings....forgot to mention, the car runs fine, if it matters....

 

The car running OK seems to point to a bad cat or O2 sensor (the sensor after the cat). A bad A/F sensor can cause fuel ratio issues.

 

Here are the live readings....car was just idling tho & only ran for about 5 or 10min....ECT team was between 185 to 200 degrees....I can drive it and get the readings while driving it for more accurate readings if necessary. It seems the readings weren't fluctuating very much. O2B1S1(V) was 3.???...fluctuated some, but stayed in the 3 range....O2B1S2(V) stayed below .5....even with increasing RPM to around 1500 I think....

 

Update: The car was NOT running fine as I thought. While driving it had a noticeable loss of power. I replace the cat earlier in the week. It's been thru a few drive cycles & the code remains gone. Power is restored. Oh, I stated the incorrect mileage in the beginning. It has 109K miles, NOT 190K. So the cat didn't last very long, I suspect because of the oil usage, right??

 

Great job!

Oil burning can reduce converter life.