O2 sensor minimum voltage high

First, I’d like to say my 2010 Tacoma 2.7L has been running great. Got my Bank 1, sensor 2 replaced by my dealer a little less than a year ago which I thought would clear my check engine light. Unfortunately I wasn’t out the door more than 50 miles and the check engine snapped back on. My OBD2 code reader came up with PO 138 pointing to the O2 sensor circuit again. Data from the sensor reflected a fail with the minimum sensor voltage being 0.82 volts where in fact the min/max voltages should be between 0.00 volts and 0.214 volts respectively - those numbers according to my code reader. Checked my gas cap, checked for bad sensor, no short circuit, all looks good. Could a bad Bank 1 sensor 1 A/F fooling the downstream O2 sensor?.....but not any other codes? What should I check next?

 

I had a similar situation on my 2007 JK (never resolved it). Issues that I was told that would set the fault are:

Bad fuel injector
Air leak up-stream - head gasket, header flange ----
Bad Catalectic Converter.
Damaged wiring.
I've also heard the some aftermarket sensors will not function correctly.

Good Luck My Friend.

 

http://www.customtacos.com/tech.old/files/05FSM/repair.html