I have a 2001 4 Runner SR5 4x4 auto with the 3.4 24 valve.
I have a 1135 error code im pulling with my code reader. My book states that its "front main O2 sensor signal faulty". I went to Autozone and they sold me a sensor. They stated that it needed to be replaced at bank 1 sensor 1. I just wanted to make sure the location of this is 1st sensor after the manifold driver side. Please make sure I am doing this right. Sensor was $189.00 and I want to make sure that I have the right stuff, location and right part for error code im pulling.
Thanks,
JayBronco

 

I would check the wiring to the O2 sensor prior to replacement make sure the insulation on the wires is entact and any engine grounds are clean and tight. A faulty signal does not necessary mean the O2 sensor is bad .... just that the voltage signal from the O2 sensor is not in parmeters with the ecu.

 

But to answer the question, Bank 1 Sensor 1 is forward of the cat or cats. Sensor 2 is after the cat (or after the last of two). I believe all 2001's had 2. Yours should be a Denso 234-9002, right? I don't have a lot of confidence in Autozone for this. So I am curious if you have the right one...

 

make sure you have an air fuel sensor not an o2 sensor

[you will know because the connector won't fit]

and yes it is the before cat sensor

 

Thanks guys,
I put the o2 sensor in and after resetting the code to turn the light off it has worked. I checked the wiring and contacts all were fine and clesn. Where i was most confused was the schematic (sp?) I was given at Autozone. It showed 4 sensors were I only saw 2. I had the right one and so far it has worked, keep your fingers crossed.
Thanks for the followups.
JayBronco

 

you will know by 3 tanks of gas if it will stay working. if the plug fit, it was the right part. and 1135 is the
heater circuit on the sensor itself. nothing has to be wrong with anything else for those to fail... they just die.

 

Well 1 tank of gas down. So far so good.
Thanks Again,
JayBronco