P0135 and P0141 after replacing both O2 sensors, 2000 4Runner

[Paddo]

Hi everyone,
I'm new here. I have a 2000 4Runner Limited (non-California spec exhaust). As the title suggests, I replaced both O2 sensors a few days ago, after my Check Engine light came on. I took it to AutoZone and that's what the guy said I should do (Codes P0135 and P0141). So I swapped them out, took it back to have the codes cleared, and the light came back on after the second start.

I've been searching for a few days now, trying to figure out what the problem could be since replacing the O2 sensors didn't help (seemed odd that both would fail at the same time, too). I'm beginning to worry it could be a wiring issue, which I don't have a lot of experience with. Any other ideas? I appreciate the help.

-Paddo

 

[Vandy756]

Having same issue here. Help would be much appreciated.

Hey guys, so I'm getting O2 sensor codes P0141 and P0135 (heater circuit). They are both brand new Denso sensors, originally replaced because the other two were bad. Anyway, I had no issue from the new ones until I had my headers redone. Redone as in fixed a couple of small leaks and powder coated. After I installed them, I started getting the codes. I pulled them out and whiped them off, sprayed the connectors with electrical connector cleaning agent. Still getting the codes. I even had the codes cleared after pulling them out to clean. I went 160 miles with no problem. Woke up one morning to go to work and it came on before I even pulled out of the garage. Someone mentioned that I am suppose to have four sensors. I notice an additional spot for a third sensor on the y pipe but it has a plate bolted over the hole. Is there suppose to be another? Any advice? I've been dealing with this for three weeks now.

 

[Paddo]

I'm not sure about the 4-sensor setup. If my memory is correct, that's only on the California-emissions-compliant exhaust systems. Mine is a 49-state (not CA compliant) so it only has the two sensors. One upstream (before the catalytic converter) and one downstream (after the cat).

In my case, the problem ended up being the engine control computer, which ran me about $200 for a used one (I think - this was 4 years ago though). It didn't seem to affect the way the car drove, but probably slightly negatively affected my fuel economy. I had to get it fixed to pass emissions, though, so I could register my car in Maricopa county.

Here's my other thread on the topic: http://www.toyota-4runner.org/3rd-gen-t4rs/173691-pcm-failure.html