Here is the graph from me idling after doing a lot of driving. This was the result after about 20 minutes of highway driving after 40 minutes of regular driving. It seems to be about the same. The downstream has too much activity with the upstream not having enough. I noticed that when I release the throttle the upstream sensor goes high and the downstream goes low for a bit before going back to regular
based on the incomplete data Iāve seen so far . . . you still havenāt shown fuel trims and loop status, for example . . . that upstream sensor is shot
P0420 sets when the downstream sensor fluctuates at a rate nearly the same rate . . . around 80% . . . as the upstream sensor
Whateverās going on with the cat, I still think you need to replace the upstream sensor first and retest
The cat may very well be degraded enough to cause that code to set, but Iād start with the small stuff first
I donāt really have a way to monitor the loop status after I begin driving, all of this graphed data is captured while Iām driving and viewed later. I just know that the loop status goes to closed after around 15-25 seconds after turning the car on (a guess, donāt take those numbers as fact). Anything after I start driving is unknown to me. Attached is the same drive as last post, with the O2S1 Short term Fuel trim data plotted as well. I will post LTFT tomorrow when I go out again. I am planning on buying new O2 sensors, both if they arenāt too expensive and will replace them both when they arrive, since if one went out the other probably isnāt the farthest behind. I will re-evaluate afterwards. I donāt need the catalyst to be the most efficient in the world, just efficient enough to get inspected for the year. My hope is that a new upstream O2 sensor will work correctly and begin fluctuating just enough so that the downstream sensor fluctuating isnāt enough to set off the code.
The time line in those recordings is rather compressed, you have 2 minutes of data packed into each recording, that makes it difficult to judge the reaction of the sensors.
Reduce the increments from 20 seconds to 5 seconds, record the data at a steady 2000 RPMs, donāt snap the throttle, we canāt see the TPS value to know why there are big spikes in the graph.
Okay, just so Iām sure I get everything tomorrow. You guys want a graph from the car after some heavy driving so everything is warm, with the engine at a steady 2000RPM, showing the TPS, short term fuel trim, and both O2 sensors, with as much data was I can show with 5 second intervals? Along with that I should state the Long term fuel trim and the loop status at the time of the recording?
5 minutes of normal driving is sufficient. If you donāt snap the throttle open/closed there is no need for TPS display, snapping the throttle produces an erratic display, it shows the range of the oxygen sensors but makes for a confusing display.
I only mentioned the snap throttle test as a possible means of gauging the upstream oxygen sensorās present condition
And from what Iām seeing . . . so far . . . Iām really beginning to think the upstream sensor is done for
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Hello everyone. Hereās the data I would get today. Everything was taken with the engine hot directly after driving and at a (mostly) steady 2500RPM.
Top graph in this picture is the STFT:
So I got the new O2 sensors and installed them today. I did some driving and I still got a pending P0420 code. The upstream graph had more activity and more definitive ups and downs, but it was still within that 0.48 to 0.53V range. Could it be a wiring problem? Iām beginning to stress though, because Iām going to college in about a week and would really like to have this problem situated and donāt have the real means to replace the cat at the momentā¦
Anyone know of ways to get the cat to be just a little more efficient temporarily, just so I can get my car inspected for the year, I just need more time to get everything situated before I can begin putting money like that into my car.
you could try a product named Cataclean or something like this: