Faulty upstream O2 sensor (Bank 2, Sensor 1) (45% likelihood): The upstream oxygen sensor on Bank 2 has failed or degraded, producing an erratic, stuck, or out-of-range signal that the PCM identifies as a circuit malfunction. Damaged or corroded wiring/connector (25% likelihood): The sensor's wiring harness or electrical connector has been damaged by heat, corrosion, or physical contact, causing an intermittent or faulty connection. Exhaust leak before the sensor (15% likelihood): An exhaust manifold leak or cracked exhaust pipe upstream of the sensor allows outside air to enter, causing false readings. Vacuum leak affecting Bank 2 (10% likelihood): A vacuum leak on the intake side of Bank 2 can cause a lean condition that the sensor reads abnormally, though this usually sets fuel trim codes as well. PCM or ground circuit fault (5% likelihood): A faulty PCM input circuit or poor sensor ground connection can prevent proper reading of the sensor signal.

How much does it cost to fix P0150?

DIY repair typically costs $30–$200 for parts. Professional repair runs $150–$500 including parts and labor.

P0150

Powertrain

Moderate

O2 Sensor Circuit Malfunction (Bank 2, Sensor 1)

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The P0150 code indicates a general circuit malfunction with the upstream oxygen sensor on Bank 2 — the side of the engine opposite cylinder #1 on V-configuration engines. This is the primary oxygen sensor that the PCM uses to monitor and adjust the air-fuel mixture for Bank 2 cylinders. Because this sensor directly influences fuel trim, a malfunction can noticeably affect engine performance.

You may notice reduced fuel economy, rough running, hesitation during acceleration, or a rough idle. The engine may run rich or lean on Bank 2 since the PCM cannot properly read the exhaust oxygen content. The check engine light will be on and the vehicle will fail emissions testing.

This is a moderately urgent repair because an improperly functioning upstream O2 sensor can cause the engine to run with an incorrect air-fuel ratio, potentially leading to catalytic converter damage over time. Start by inspecting the sensor's wiring and connector for damage, then check for exhaust leaks near the manifold. If these check out, replace the sensor. Upstream O2 sensors are generally accessible from the top of the engine bay or underneath the vehicle near the exhaust manifold.

Severity

Moderate — Address SoonThis Week

Symptoms

•Check engine light is on
•Reduced fuel economy
•Engine may run rough or hesitate on acceleration
•Possible rough idle
•Vehicle fails emissions testing
•Exhaust may smell rich or have a fuel odor

Likely Causes

Faulty upstream O2 sensor (Bank 2, Sensor 1)45%

The upstream oxygen sensor on Bank 2 has failed or degraded, producing an erratic, stuck, or out-of-range signal that the PCM identifies as a circuit malfunction.

Damaged or corroded wiring/connector25%

The sensor's wiring harness or electrical connector has been damaged by heat, corrosion, or physical contact, causing an intermittent or faulty connection.

Exhaust leak before the sensor15%

An exhaust manifold leak or cracked exhaust pipe upstream of the sensor allows outside air to enter, causing false readings.

Vacuum leak affecting Bank 210%

A vacuum leak on the intake side of Bank 2 can cause a lean condition that the sensor reads abnormally, though this usually sets fuel trim codes as well.

PCM or ground circuit fault5%

A faulty PCM input circuit or poor sensor ground connection can prevent proper reading of the sensor signal.