Hello everyone, I am new to this forum and I have a question if anyone can help me figure this out. So my 2001 4runner is due for emission this year and I had a check engine light telling me to change the air/fuel sensor ( at the time that was the only code that came up). I changed the sensor and cleared the light. Everything went well for a couple of days and my light came on again and now it's giving me a p0420 which is the cat efficiency code. I know this could either be the rear O2 or the cat so I went and run a test on both the air/fuel sensor and the rear O2 sensor. the rear seems to be giving me the correct voltage of about 1.5 give or take a little but the air/fuel sensor is giving me like over 3. Does that seems right? I'm not sure how much its suppose to give and if its not what do you think the problem might be. Any help would be greatly appreciated. Thank you
New Member question P0420 code :(
- Thread starter huyroy
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SweetWaterSurprise
Banned
Had the same code and it was the rear O2. Swapped it out without further issue.
jgue467
Senior Member
What was the first code you got that lead u to replace a/f?
Service manual sez these are potential faults (in order of diagnosis):
1. Gas leakage on exhaust system (cause of mine)
2. A/F sensor (bank 1 sensor 1)
3. Heated oxygen sensor (bank 1 sensor 2)
4. Three-way catalytic converter
The tests for the 2 sensors is ohm based, see page 980-81 for values.
I forgot what code it was P1135 maybe? it said air fuel sensor bank 1 sensor 1. I am working on take off the rear O2 sensor but it's really in there and still not sure how I am gonna remove it (any ideas?). Another question though, I know the 4runner has 2 cats so how do you know which one to replace if it comes down to the cats. Car only has one bank and one cat follows the other. I am new to this car and still has lots to learn about it. Thanks
TheDurk
Elite Member
Don't celebrate until you run a full tank of gas through it--or, better yet--scan it and get an 'ALL TESTS COMPLETE' feedback on it.
It takes a while, sometimes quite a while, to complete that cat efficiency test.
It was done a few days ago, ran about 130 km and still no codes. Brought in to get my e-test and it passed no problem.
Just to go through the entire process of what lead me to using the non-foulers.
I ran out of gas at 1/4 tank on the gas gauge about 2 months ago.
Got gas back in it and the CEL as well as the trio of lights including VSC/TRAC were illuminated on the ride home and consequently for about 1 1/2 months. P0430 was the code.
I replaced the gas cap. Didn't fix it.
Took it to Toyota and they told me it was the bank 2 #1 & #2 as well as the bank 1 #2 sensors and a bad fuel sending unit. Their price? $1400 with about $800 in parts and $600 in labor. NO THANKS.
Put in a quart of Lucas Oil Injector Cleaner. Nothing, still had the CEL.
I replaced the sensors (I wish I hadn't) myself after getting them from O'Reilly ($270 for all with my brother's employee discount). Light still didn't go off.
Did the spark plug non-fouler fix on the bank 2, #2 sensor. Did a poor man's reset and the problem went away. I'm 460 miles in and passed my TX inspection the day I did the fix.
I doubt that this is always the case and that the non-foulers may not always work. However, I tried a lot of different avenues before doing it and I wish I had started with it. My next steps were to get the injectors pressure cleaned and possibly tested and/or replaced. Glad I didn't have to go that far.
I ran out of gas at 1/4 tank on the gas gauge about 2 months ago.
Got gas back in it and the CEL as well as the trio of lights including VSC/TRAC were illuminated on the ride home and consequently for about 1 1/2 months. P0430 was the code.
I replaced the gas cap. Didn't fix it.
Took it to Toyota and they told me it was the bank 2 #1 & #2 as well as the bank 1 #2 sensors and a bad fuel sending unit. Their price? $1400 with about $800 in parts and $600 in labor. NO THANKS.
Put in a quart of Lucas Oil Injector Cleaner. Nothing, still had the CEL.
I replaced the sensors (I wish I hadn't) myself after getting them from O'Reilly ($270 for all with my brother's employee discount). Light still didn't go off.
Did the spark plug non-fouler fix on the bank 2, #2 sensor. Did a poor man's reset and the problem went away. I'm 460 miles in and passed my TX inspection the day I did the fix.
I doubt that this is always the case and that the non-foulers may not always work. However, I tried a lot of different avenues before doing it and I wish I had started with it. My next steps were to get the injectors pressure cleaned and possibly tested and/or replaced. Glad I didn't have to go that far.
