If only bank 2 is lean, the issue is likely specific to that side — a vacuum leak, exhaust leak, or bad sensor on that bank.

Can I swap bank 1 and bank 2 sensors to test?

Yes — if the code follows the sensor, the sensor is bad. If it stays on bank 2, the problem is something else.

P0151

Medium Severity

Emissions System

Upstream O2 sensor on bank 2 is stuck low, reading lean.

Common Fix

Replace O2 sensor

Estimated Cost (DIY)

$30 - $100

Failed O2 sensorlikely

Vacuum leak on bank 2possible

Exhaust leak near sensorpossible

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Why only bank 2?: If only bank 2 is lean, the issue is likely specific to that side — a vacuum leak, exhaust leak, or bad sensor on that bank.
Can I swap bank 1 and bank 2 sensors to test?: Yes — if the code follows the sensor, the sensor is bad. If it stays on bank 2, the problem is something else.

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