Code result
P0040
O2 Sensor Signals Swapped Bank 1 Sensor 1 / Bank 2 Sensor 1
Moderate severity
What it means
The pre-cat oxygen sensors of bank 1 and bank 2 appear to be wired the wrong way around — bank 1 reacts when bank 2 should and vice versa. Typically after recent service.
Is it safe to drive?
Use caution
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical.
Most likely causes
Sensors swapped after recent replacement
highOne of the most commonly reported causes for this code — check this first.
Wiring harness routed across banks
mediumA plausible cause — test and verify before replacing parts.
Related help
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