P0041Medium SeverityEmissions

O2 Sensor Signals Swapped (Bank 1 Sensor 2 / Bank 2 Sensor 2)

What This Means

The downstream oxygen sensor signals for bank 1 and bank 2 appear to be reversed. The catalyst monitoring sensors are connected to the wrong banks.

Common Symptoms

Incorrect catalyst monitoring
Check engine light on
Failed emissions test
No drivability symptoms

Common Causes

Sensor connectors swapped during service
Wiring error
Incorrect sensor routing
Aftermarket exhaust installation error
Harness mislabeled

Estimated Repair Cost

$50 – $300

Parts and labor (varies by vehicle and location)

Difficulty:Easy

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For informational purposes only. Diagnostic trouble codes are starting points for diagnosis, not definitive answers. Always consult a certified mechanic for proper diagnosis and repair. Estimated costs vary by vehicle, location, and shop rates.