TFJ-4runner
New member
I wanted to share my experience with these two codes and how I resolved these two issues. I bought my 4runner a few weeks ago after verifying the codes before handing him cash for the vehicle. The scanner read only a P0420 code at the time of purchase.
I drove home a little over nine hours and was sure to listen for misses or anything out of the ordinary. Once I made it home and found the time I started digging into threads or websites with anything to do with these codes. Anything that mentioned these codes, O2 sensors, or what makes a catalytic converter go bad I probably read.
P0420 Code:
Catalyst System Efficiency Below Threshold (Bank 1)
P0430 Code:
Catalyst System Efficiency Below Threshold (Bank 2)
Anything that mentioned the 2UZ motor and this condition had very different answers as to what the cause was. Most people that sought help from Toyota were told that both bank 1 and 2 catalytic converters needed to be replaced. At 140K miles I could see this being a possibility but not likely.
This engine in particular runs very clean and even with these codes was maintaining a excellent idle and had great rpm increase throughout WOT shifts. It was hard for me to believe that with the condition of the engine that it would cause the cats to foul out now.
I did the following suggested things in order and also just from the knowledge I've gained throughout the years.
1: Cleared the code and noted how long it took to come back on and noted it
2: Once the code was back the car was given two cans of sea foam and cleared again. This was to clean out the internals of the engine and to also check for exhaust leaks using the smoke that comes out after the chemical is burned. I had no exhaust leaks so I kept seeking possibilities cheaper to more expensive.
3: There are two O2 sensors per bank. On the 2UZ the Driver side is bank one. I replaced the upstream first due to it being the most likely to go out from what I researched. It kept the CEL off for 67 miles and then came back on.
4: I then changed the downstream sensor and the vehicle went to 71 miles before throwing another code. This time for P0430 and P0420. This was confusing to me as to why it would not only trigger bank 1 but then trigger bank 2. I cleared the code and attempted another driving cycle.
5: 108 Miles and the light again came on again but this time only for P0430. I was excited at this point because I wasn't going to have to spend $1600 per bank on replacement Catalytic converters. I cleared the code and went 60 miles completing the drive cycle and was able to pass emissions. 44 Miles later the CEL for P0430 came on and I decided to go ahead and replace the bank 2 downstream O2 sensor.
6: It has now been over 300 miles of mixed driving and some WOT. "I'm still trying to clean out 140K miles of soccer mom driving" I have not got a CEL code for any bank and the engine runs excellently. My gas mileage is much better and I have to say the O2's being bad had a lot to do with that.
I know this is a long read but the most frustrating thing for me was that there was so many others that have had this issue but not many updates once the issue had been resolved. I ended up spending around $250 in O2's and other things to help diagnose this problem. I just want to put this out there for the next person that has this issue come up. These vehicles are getting to the age where it is likely they will get these codes. I ended up getting lucky doing research and doing the right steps to figure it out successfully. It saved me thousands of dollars and a lot of stress. Patience is key with this process but it was worth it looking back. It took me 7 days of diagnosing to get this all resolved. Hope this helps others out in the future.
TFJ
I drove home a little over nine hours and was sure to listen for misses or anything out of the ordinary. Once I made it home and found the time I started digging into threads or websites with anything to do with these codes. Anything that mentioned these codes, O2 sensors, or what makes a catalytic converter go bad I probably read.
P0420 Code:
Catalyst System Efficiency Below Threshold (Bank 1)
P0430 Code:
Catalyst System Efficiency Below Threshold (Bank 2)
Anything that mentioned the 2UZ motor and this condition had very different answers as to what the cause was. Most people that sought help from Toyota were told that both bank 1 and 2 catalytic converters needed to be replaced. At 140K miles I could see this being a possibility but not likely.
This engine in particular runs very clean and even with these codes was maintaining a excellent idle and had great rpm increase throughout WOT shifts. It was hard for me to believe that with the condition of the engine that it would cause the cats to foul out now.
I did the following suggested things in order and also just from the knowledge I've gained throughout the years.
1: Cleared the code and noted how long it took to come back on and noted it
2: Once the code was back the car was given two cans of sea foam and cleared again. This was to clean out the internals of the engine and to also check for exhaust leaks using the smoke that comes out after the chemical is burned. I had no exhaust leaks so I kept seeking possibilities cheaper to more expensive.
3: There are two O2 sensors per bank. On the 2UZ the Driver side is bank one. I replaced the upstream first due to it being the most likely to go out from what I researched. It kept the CEL off for 67 miles and then came back on.
4: I then changed the downstream sensor and the vehicle went to 71 miles before throwing another code. This time for P0430 and P0420. This was confusing to me as to why it would not only trigger bank 1 but then trigger bank 2. I cleared the code and attempted another driving cycle.
5: 108 Miles and the light again came on again but this time only for P0430. I was excited at this point because I wasn't going to have to spend $1600 per bank on replacement Catalytic converters. I cleared the code and went 60 miles completing the drive cycle and was able to pass emissions. 44 Miles later the CEL for P0430 came on and I decided to go ahead and replace the bank 2 downstream O2 sensor.
6: It has now been over 300 miles of mixed driving and some WOT. "I'm still trying to clean out 140K miles of soccer mom driving" I have not got a CEL code for any bank and the engine runs excellently. My gas mileage is much better and I have to say the O2's being bad had a lot to do with that.
I know this is a long read but the most frustrating thing for me was that there was so many others that have had this issue but not many updates once the issue had been resolved. I ended up spending around $250 in O2's and other things to help diagnose this problem. I just want to put this out there for the next person that has this issue come up. These vehicles are getting to the age where it is likely they will get these codes. I ended up getting lucky doing research and doing the right steps to figure it out successfully. It saved me thousands of dollars and a lot of stress. Patience is key with this process but it was worth it looking back. It took me 7 days of diagnosing to get this all resolved. Hope this helps others out in the future.
TFJ
