7:32 am
Club Member
January 20, 2009
Offline
Long story short, I got the dreaded P0420. New cats, new O2 sensors, new thermostat (got a different code for that one). Everything passes the smog check on my scanner except the oxygen sensor test will not complete. I’ve driven a lot of miles and tried the 40-60-40mph tip. Besides registering in a no smog county/state, are there any other tips to get the oxygen sensor test to complete so I can pass smog?
Next will be to drop it off at Folsom Jeep if I can’t figure it out.
9:19 am
Club Vice President
June 11, 2021
Offline
OH man! Sorry to hear this! 
Let us know how it goes.
Buck is fighting a lot of red tape for his rig as well.
L 
"No beans!"
2:07 pm
Club Member
July 14, 2016
Offline
If you have to take it to a shop, take it to Applegate garage. The owner Zach is awesome. Check out their reviews online. Plus he is an off road guy. Call the shop and ask to talk to Zach and tell him what you've done. He will give you tips and that way you can get a feel for him and his shop before going there, should you do need to take it in. Tell him that I recommend you.
9:12 am
Club Treasurer
April 2, 2003
Offline
Getting the last code to clear took me more than 40 miles of driving on back country roads, but it eventually registered all green. I drove around Loomis, Lincoln, Auburn area. Their back roads seemed to be the best speed for my criteria to register. I just kept the reader in my jeep and checked it every 30 mins or so.
10:14 am
Club President
March 13, 2015
Offline
I use fast Freddy’s for smog at the shingle springs exit. O2 was the only thing that wasn’t ready. He sent me out on a short drive down north shingle road about half way to Lotous holding 40mph. Got back and it had worked.
2:50 pm
Club Member
July 10, 2003
Offline
What Brad said... drive the crap out of it on the back roads.
I used to wheel a lot. . .
10:13 am
Club Member
October 28, 2016
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Yeah I drove for over a year without even knowing my o2 wasn’t running. The little ding check engine in the run position has been going off since I changed my battery I just didn’t know what it meant.
Those instructions I sent you were done on green valley road.
Thompsons Jeep was really cool about the whole thing and worked hard with corporate but mine was under warranty. New o2 sensors and pcm did nothing. Maybe luck was the final result of it passing.
W6JLU
12:37 pm
Club Member
January 20, 2009
Offline
kris_olof said
I use fast Freddy’s for smog at the shingle springs exit. O2 was the only thing that wasn’t ready. He sent me out on a short drive down north shingle road about half way to Lotous holding 40mph. Got back and it had worked.
Any specific RPMs or just regular driving? I’ll keep trying different things a little longer.
3:22 pm
Club Member
January 20, 2009
Offline
Just thought I would post a follow up. I eventually passed smog. I disconnected and reconnected the PCM connectors and the O2 sensor test completed.
Coincidence? Who knows, but something to try if you run into the same issue.
6:25 pm
Club Member
March 5, 2015
Offline
You gotta love modern technology
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