What the P0138 code means?
P0138 is the OBD-II generic code indicating the O2 sensor for bank 1 sensor 2 fails to have a lower voltage output below 1.2 volts for more than 10 seconds indicating a lack of oxygen in the exhaust stream.
What causes the P0138 code?
Faulty O2 sensor
Short to battery voltage in O2 sensor signal circuit
High fuel pressure
What are the symptoms of the P0138 code?
These could include a lean or rich condition in the engine, decreased fuel efficiency, black smoke from the
tailpipe, and an illuminated service engine soon lamp.
Common mistakes when diagnosing the P0138 code:
Technicians report replacement of oxygen sensors, when lean or rich engine conditions are the cause of
incorrect readings, is fairly common. Replacement of the incorrect oxygen sensor is also a possibility.
What repairs can fix the P0138 code?
Replacing the O2 sensor for bank 1 sensor 2
Repairing or replacing the wiring or connection to the O2 sensor for bank 1 sensor 2
Replacing the catalyst in front of the sensor
Repairing a leaking injector