What does OBD2 code P0138 mean?+
P0138 stands for O2 Sensor Circuit High Voltage Bank 1 Sensor 2. Downstream O2 sensor on Bank 1 reading consistently high voltage.
What causes code P0138?+
Failed downstream O2 sensor; Rich exhaust passing through cat; Fuel-contaminated catalyst; Faulty sensor
How do I fix code P0138?+
Replace downstream O2 sensor; Check for rich condition upstream; Test catalytic converter; Inspect fuel injectors for leaks
How much does it cost to fix P0138?+
Estimated repair cost for P0138 is $100–$350.
Is P0138 DIY-friendly?+
Yes — P0138 is generally DIY-friendly with basic tools.