A failed or degraded bank 2 upstream oxygen sensor; A damaged or corroded sensor wiring harness or connector; A blown fuse that supplies power to the oxygen sensor heater circuit; An exhaust leak before the sensor that allows outside air to skew the reading; A faulty engine coolant temperature sensor that confuses the computer's fuel strategy; A vacuum leak or intake leak that affects bank 2 more than bank 1; A problem in the engine computer itself, though this is rare

DTC codes / P01xx · Fuel and air metering / P0150

P0150O2 Sensor Circuit Malfunction (Bank 2 Sensor 1)

Q: What does code P0150 mean?

O2 Sensor Circuit Malfunction (Bank 2 Sensor 1). P0150 means the engine computer has detected an abnormal signal from the upstream oxygen sensor on bank 2, the side of the engine that does not contain cylinder number one. The sensor is responsible for reporting the oxygen content in the exhaust before the catalytic converter, and the computer sees a voltage or circuit condition that does not match what a healthy sensor should produce.

P0150 means the engine computer has detected an abnormal signal from the upstream oxygen sensor on bank 2, the side of the engine that does not contain cylinder number one. The sensor is responsible for reporting the oxygen content in the exhaust before the catalytic converter, and the computer sees a voltage or circuit condition that does not match what a healthy sensor should produce.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
A noticeable drop in fuel economy as the computer defaults to a rich fuel mixture
Rough idle or hesitation during acceleration because fuel delivery is no longer accurately trimmed
An increase in tailpipe emissions that may cause a failed emissions inspection
In some cases, a sulfur or rotten egg smell from the exhaust due to excess fuel reaching the converter

Common causes, most likely first

A failed or degraded bank 2 upstream oxygen sensor
A damaged or corroded sensor wiring harness or connector
A blown fuse that supplies power to the oxygen sensor heater circuit
An exhaust leak before the sensor that allows outside air to skew the reading
A faulty engine coolant temperature sensor that confuses the computer's fuel strategy
A vacuum leak or intake leak that affects bank 2 more than bank 1
A problem in the engine computer itself, though this is rare

How to diagnose and fix it

Scan all stored and pending codes to confirm P0150 is the only oxygen sensor code and check for related misfire or fuel trim codes
Inspect the bank 2 upstream oxygen sensor wiring and connector for chafing, corrosion, or loose pins
Check the oxygen sensor heater circuit fuse and verify power and ground at the sensor connector with the key on
Use a scan tool to watch live bank 2 upstream oxygen sensor voltage and compare it to bank 1 upstream sensor behavior
Perform a smoke test or visual inspection for exhaust leaks between the cylinder head and the sensor location
Replace the bank 2 upstream oxygen sensor if the circuit and live data confirm the sensor is not responding correctly
Clear the codes and complete a drive cycle to verify the repair and confirm the monitor runs without resetting the code

What the code does not always mean

A P0150 is frequently set by a wiring problem rather than a dead sensor, so inspect the harness near hot exhaust components before buying a new sensor.
An exhaust leak just ahead of the sensor can pull in outside air and make a good sensor report a false lean condition, triggering this code.
On engines with two upstream sensors, a vacuum leak that affects only bank 2 can set P0150 even though the sensor itself is healthy.
A lazy sensor that responds slowly may not set a hard code until the computer runs its monitor under specific driving conditions, so the light can come and go.
Replacing the sensor without checking the heater circuit fuse can lead to a repeat failure if the fuse blows again due to a shorted wire.

Can I keep driving with P0150?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration or long trips because the engine may run rich and damage the catalytic converter over time. If the check engine light begins flashing, stop driving and have the vehicle towed.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.