P0040O2 Sensor Signals Swapped Bank 1 Sensor 1/Bank 2 Sensor 1
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.
Can I keep driving? With caution
You can drive to the shop, but do not postpone the repair. The problem may worsen and damage other components.
Sistema Afectado
Aire / Combustible · Inyección, MAF, MAP, O₂
Relacionado con la mezcla aire-combustible: sensores de flujo, presión, inyectores o bomba.
Espacio para vendedores de repuestos
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Symptoms You Will Notice
What you may observe when this code appears
- Check engine light on Increased fuel consumption Possible rough idle or hesitation Failed emissions test
Possible Causes
The components or conditions that trigger this code
- 1Sensors swapped after recent replacement Wiring harness routed across banks
How to Fix It — Step by Step
Recommended diagnostic and repair procedure
- 1Difficulty: easy. Estimated time: 0.3-1 hours. Estimated cost: €10-€
- 2DIY possible
Note: This information is for general reference. For precise diagnostics and safety repairs, always consult a certified mechanic.
Estimated Cost
Approximate range in USD (varies by region and shop)
Varies by diagnosis
* Diagnosis only: $50–$150
Quick Info
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