Hey guys.. I've been searching, and searching, and searching... and there hasnt' been a definate answer to this code. I know it's the first O2 sensor before the cat, but why does it keep throwing this code? I cleared it about a month ago, and it didn't come back for 2 weeks. I cleared it again, and it came back in 2 days. Today I got it again, and It came back in about 20 minutes! (I'm pulling the negative off the battery).
I have Inspections due this month, and I was going to do it at the end of the month... should I just pull the negative and take it to inspections? Or is there an easier fix. Somebody posted something about a simulated O2... anybody got any idea what that is? I couldn't find an exact answer or how to. Thanks in advance guys.
Btw, it's a 2000 Cavalier Z24, 2.4L Twin Cam (automatic).
It's the O2 after the cat.
P0420 OBD Trouble Code
Technical DescriptionCatalyst System Efficiency Below Threshold (Bank 1)
What does that mean?Basically this means that the oxygen sensor downstream (after) the catalytic converter on bank 1 is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.
Symptoms: You will likely not notice any drivability problems, although there may be symptoms.
Causes: A code P0420 may mean that one or more of the following has happened:
Leaded fuel was used where unleaded was called for
An oxygen sensor is not reading (functioning) properly
The engine coolant temperature sensor is not working properly
Damaged exhaust manifold / catalytic converter / exhaust pipe
Retarded spark timing
Possible Solutions: The simplest thing to do is to reset the code and see if it comes back.
Next step is to measure the voltage at the oxygen sensor on Bank 1 (the rear sensor, or the sensor after the converter). The voltage should be low and steady (~200mV, depends on the vehicle). If the voltage varies (e.g. 100mV to 600mV) then it's time to replace the catalytic converter. In fact, it would be a good idea to test each oxygen O2 sensor while you're at it.
One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.
Need more help?If you still need help regarding this trouble code, please post your concern in the forums.
http://www.obd-codes.com/forums/index.php
But people on the Org recommend NOT replacing the cat, unless it really is dead. I read some people do O2 sims......... any input anybody?
I had a weld shop drill a hole and weld on an O2 sensor bung (aft cat is 18mm fine thread) on my after market high-flow cat, exactly where the OE sensor was. Engine breathes better, and no codes! Emmission inspections never know it's there.
I guess nobody can help me...
I just started to get this code myself. I changed the O2's 1 year ago. The vehicle has about 110000 miles on it. Should i just change the cat?
i had the sam code like 3 years ago....i started looking in to it and looking over the car and found that the converter was loose inside.......hence the 420.....
