2005 4runner P0138 code

[parsky1]

I just got a P0138 code. Oxygen Sensor Bank 1 Sensor 2 high voltage. I looked at the voltage with the scan tool and both Bank 1 Sensor 2 and Bank 2 Sensor 2 read about 0.75V. I then went to look at the Service $06 Tests and it shows that Bank 1 Sensor 2 failed TID $07 which is a minimum and maximum voltage check. Minimum voltage read was .722 while maximum expected was 0.195V

Thoughts?

 

[BOSMECH]

Change them out.
You can get them on amazon.com for cheap.
Get Denso, Bosch will mess the truck up.

 

[bagginz]

I just got a P0138 code. Oxygen Sensor Bank 1 Sensor 2 high voltage. I looked at the voltage with the scan tool and both Bank 1 Sensor 2 and Bank 2 Sensor 2 read about 0.75V. I then went to look at the Service $06 Tests and it shows that Bank 1 Sensor 2 failed TID $07 which is a minimum and maximum voltage check. Minimum voltage read was .722 while maximum expected was 0.195V

Thoughts?

This code is almost always just a faulty sensor. Sometimes they can be tricky to diagnose. Id just replace the sensor

 

[parsky1]

Changed it out today with the recommended Denso replacement. Checked codes before I reset the ECU. I guess I also got a P0136 at some point after the P0138 code. Took it for a drive and I did notice while driving that I see a lot more activity on the Bank 2 sensor. Bank 1 sensor hardly moves and is still a higher voltage. Bank 2 was usually 0.66-.078 while Bank 1 (which is the sensor I just changed) was still around 0.78V with little activity.

Sat in the driveway with it idling after driving at bank 1 sits a 0.78V while bank 2 will move around 0.3 to 0.7 as I rev the engine and then let it idle. Bank 1 and Bank 5 wide range upstream sensor voltages look normal and track each other with engine rpm. Both around 3.3 to 3.4V.

I'll need to drive it again to see if it throws the code again. Also, Bank 1 is the driver's side on a V8 correct?

 

[parsky1]

Threw the same code again tonight after about 10min of driving. Bank 1 sensor 2 is basically stuck at 0.78V while Bank 2 Sensor 2 moves around generally between 0.3V and 0.7V depending on engine rpms. Seems like something else is going on here.

 

[parsky1]

Ok,

So I swapped the Bank 1 sensor 2 to the bank 2 sensor 2 position and vise versa. Still got the same P0138. I did notice while driving that the emissions test runs and forces a lean condition. Bank 1 sensor 2 will stay rich while bank 2 sensor 2 will go lean. While parked if I rev the engine to 4,000 rpms and let off the throttle I can force both sensors to go to 0.2V (lean). I'm wondering if the bank 1 Cat isn't bad?

Help!

 

[parsky1]

Going to try to measure catalytic converter temps tonight with an IR temp sensor.

 

[parsky1]

Checked outlet temp of first catalytic converters on each side with an IR temp sensor. That was the closest I could get to a shell temp. Bank 1 was running at 530F and Bank 2 was running at 575F. Looks like I might have a bad cat. :moping:

 

[parsky1]

Bad sensor was actually Bank 1 Sensor 1, which is the Air Fuel sensor. I knew it had to be either a bad cat or a lean biased A/F sensor. Turns out it was the latter. So much for accurate diagnostics...

 

[BlackWorksInc]

Bad sensor was actually Bank 1 Sensor 1, which is the Air Fuel sensor. I knew it had to be either a bad cat or a lean biased A/F sensor. Turns out it was the latter. So much for accurate diagnostics...

Diagnosing AFR sensors is a *****, you can't really range them/snap them like you do Oxygen Sensors, still trying to find more accurate methods for testing them myself.