plus 1 on the zero point calibration try.
If that doesn't work I would start pulling codes to see if there is anything that comes up, not likely since I would expect the check engine light to be on as well.
For what it's worth, if you didn't want to rig up your own wires to do the at-home zero-point calibration I can confirm that this OBDii scanner from amazon will perform the zero-point cal successfully. Not the most intuitive thing to use, but you can search it up on youtube and there is a guy that walks through the steps of clearing out the stored settings and running the zero point cal using this thing :
Amazon.com
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2003 Limited V8 4runner - Slowly turning back to stock (until the next crazy idea comes along

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