P0140 and P0138 Need help

Tagged: 02 sensor

This topic has 2 replies, 3 voices, and was last updated 4 months, 4 weeks ago by hindsight.

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January 10, 2025 at 10:40 am #307992
Leonard707
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P0140- Heated oxygen sensor circuit insufficient activity sensor 2- Brand new AC Delco installed

P0138- Heated oxygen sensor circuit high voltage sensor 2

Pcv was leaking I replaced valve cover with integrated pcv, cleaned MAF, replaced MAP sensor, cleaned throttle body. I had a bunch of other codes that have been eliminated with parts I’ve replaced

This is a 2014 Chevy volt. Has anyone heard you have to calibrate or re learn the 02 sensors?
January 30, 2025 at 7:47 pm #308583
Choppy12
Participant
Im thinking short to ground somewhere in your heater harness unplug the connector and see if either of the 2 heater wires have ground with a test light I don’t know if the ppm side should because I believe in a key off state there should be no ground side switch
March 24, 2025 at 6:14 am #310162
hindsight
Participant
Check your sensor ground. An open ground will give a high voltage fault
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