mikek753

hello all,

My car is 20 years old with 210k ml. I'm in California, that required the Smog Check.
I got P0420 code and I need to pass the smog check in a week.
2 weeks ago I got the P0420 and clear the code, but it came back in a week, so I cleared again, but this reset Catalyst readiness to Incomplete, so I can't do the Smog Check.
I added Cataclean to almost empty tank and added 4 Gal, reset the code, drove 15 ml and later 30 ml.
I see the P0420 as pending.
I took screenshots from Torque app for 2 sensors at around 3ml / start cleaning process and at 15ml, cruising around 55mph
Yes, I see that 1st bank has been more hectic vs 2nd bank sensor.

What else I can do?
I plan to keep this car for another year or two if possible, but I don't want to go with expensive Catalyst replacement.

2024-05-26-20-11-25-09

2024-05-26-20-15-19-56

2024-05-26-20-15-56-69

2024-05-26-20-23-45-35

mikek753

2024-05-26-20-41-55-91

2024-05-26-20-50-07-29

Arsenii

Hello,

Both readouts look strange to be honest, they shouldn't go as high into the Rich side, the readouts should stay close to 0.45V. Try taking the readings with the engine fully warmed up and at Idle, and also compare those to the Upstream A/F sensor readouts.

Hope this helps and best of luck!

mikek753

I added Cataclean to 1/4 tank, reset the code, drove 15 ml, got P0420 as pending.
Drove 20 ml more to get Readiness in green and P0420 pending was gone.
Added full tank, another 30 ml.
Yes, after fully warm up the idle is stable and looks as expected.
I'll drive for another 60-90 ml and recheck.

I see 4V before the Cat, and 0.7V after the CAT.
Are those correct values?

Arsenii

It is quite strange, the Graphs do look good, the only thing is that the Values all are considerably higher than they should be. Typical voltage expected from an A/F sensor is about 3.2 - 3.3V, 4V would be considered Rich and the ECU would be trying to combat it. The same goes for the Downstream O2 sensors, they should be sitting at about 0.45V with a working Catalyst, not 0.75V like on your diagram, not even sure what could be causing it without any impact on the engine.

All that raises a question on how accurate is your OBD2 scan tool, could it be that it increases the values somehow..? It would be quite interesting to see the same readouts from a different, preferably Standalone scan tool, if you can get one.

Hope this helps and best of luck!

mikek753

From wired AD310 scanner before I added Cataclean, also car engine might not warmed up, at idle:
B1S2 0.17 - 0.75V
B2S2 0.05 - 0.82 V
B2S1 3.11 - 3.34V
B1S1 3.14 - 3.36 V

above range matches Torque via ELM BT
I can re check via AD310 again

mikek753

after another day 50 ml driving, the engine is hot, right after 15ml drive, in parking

Idle

parking, pressed gas to 2000 rpm

mikek753

I was about to go to Smog Check, but see P0420 as Pending, so I postponed to go to Smog Check.
The 1st full tank at about 1/2.
This if after 15ml drive on freeway, in parking, all looks good to me
just idle

just Idle

in Parking, pressed gas to 3000 RPM

in Idle from cold - 1st minute, looks Ok

just started the car

This is after night, just started the car

after cold, car was running for a min or two

Anything I can check?
Is it Ok to try to pass Smog Check with Pending code? Or should be no even Pending for the Smog Check?

Any easy way to check for air leaks?

thanks

Arsenii

A little hard to tell, but it doesn't seem to match actually, at least the A/F Sensor is sitting at a lot more reasonable output, as for the O2 sensors, Catalysts only work when they are warmed up all the way, hence the readings you get it seems, it's not possible to directly compare the scanners if other conditions are different as well, it would be helpful to compare the two directly, with the car fully warmed up and at idle.

Those readings seem all over the place, I am really starting to question the reliability of the can tool you have, as for the P0420 code to trigger, the O2 sensor readout amplitude should almost match the amplitude with no Catalyst, yours looks just about perfect even when the engine is completely cold, even though the catalyst is only designed to work when fully warmed up, hence the idea of comparing two of the scan tools you have directly, see if both produce identical outputs.

Hope this helps and best of luck!

mikek753

I replaced B1S2 O2 sensor yesterday. Took me an hour or longer, as I don't do it every 10 years.
As result driving cycle was restarted, I'm down to last Evap readiness check.
I'll know in a few days if O2 replacement was the fix.

mikek753

I passed the Smog Check ;-)
it took 3 nights to get the Evap readiness check. As it requires several cold starts after 8-12 hours.
Looks like B1S2 O2 sensor replacement (about $80 part and fast s/h) fixed my p0420 issue.