I have a problem with the downstream oxygen sensor and the ecu
I got check engine light with p0138 error code.
I scanned the scar and noticed that the voltage on the downstream oxygen sensor is constant 1.3 volts. The sensor was removed from the car and tested with a torch and a multi-meter Technically seems to work ok.
However there is something weird. I scanned the car without the sensor connected and the voltage stays the same - 1.3 volts on the ecu.
I also scanned the voltage on the o2 plug coming to the ecu.
I got 12v on the heater wires and 4.35 volts coming down to the oxygen sensor (from ecu) (positive and ground wires).
Can you please help me to diagnose what's going on ?
unless there is an open circuit and 1.3v means that the sensor is broken.
Is there anyone how could check that on their car? like unplugging the downstream sensor and checking what voltage appears one the scanner .. I know it's a lot to ask for.
How can I check the wires for shorts. You mean the hot (positive) one with both heater wires and the ground (negative) with the hot (positive) right?
I suspect that the wires are ok - already getting 12v on the heater wires and ~5v on the hot and ground (negative) wires. if there was a broken wire I couldn't get the right voltage on the plug coming from the ecu
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