OBD2 code P0040: O2 Sensor Signals Swapped Bank 1 Sensor 1/Bank 2 Sensor 1
On engines with two exhaust banks, the control module checks whether the upstream oxygen sensors are assigned to the right bank.
Detected Root Component
Oxygen Sensor
Technical Component Diagrams
Oxygen Sensor Layout
Diag Expert technical diagram
Oxygen Sensor Connector
Diag Expert technical diagram
Observed Symptoms
- Check engine light on
- Fuel trim and mixture codes possible
- Unstable idle or higher consumption possible
Possible Causes
- Sensor connectors plugged in crosswise after a repair
- Harness routed wrongly or pins swapped in a connector
- Wrong harness, control module or calibration after a replacement
Tools Required
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Parts likely to be the cause (Moteur (général))
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Frequently asked questions about code P0040
What does code P0040 mean? ▾
OBD2 code P0040: O2 Sensor Signals Swapped Bank 1 Sensor 1/Bank 2 Sensor 1. On engines with two exhaust banks, the control module checks whether the upstream oxygen sensors are assigned to the right bank.
What are the symptoms of code P0040? ▾
Code P0040 may cause: Check engine light on, Fuel trim and mixture codes possible, Unstable idle or higher consumption possible. The intensity of these symptoms varies depending on the vehicle and driving conditions.
What causes code P0040? ▾
The most common causes of code P0040 are: Sensor connectors plugged in crosswise after a repair, Harness routed wrongly or pins swapped in a connector, Wrong harness, control module or calibration after a replacement. A proper OBD2 diagnostic will pinpoint the exact cause.
Is it serious to drive with code P0040? ▾
Code P0040 has moderate severity (Warning). Short-term driving remains possible, but a prompt check is recommended to prevent worsening.
How do I fix code P0040? ▾
Start by reading the code with an OBD2 scanner, then follow the interactive decision tree on this page. Priority causes to check: Sensor connectors plugged in crosswise after a repair, Harness routed wrongly or pins swapped in a connector, Wrong harness, control module or calibration after a replacement. Difficulty: Medium · Estimated time: 30-60min.