P0040

Symptoms

• Check Engine Light Illuminates
• Increased fuel consumption
• Unstable engine operation at idle
• Reduced engine power
• Rough engine operation when accelerating
• Increased exhaust toxicity

Causes

• Incorrect installation of oxygen sensors after replacement
• Error when connecting sensor wiring
• Confusion with connectors when repairing the exhaust system
• Incorrect labeling or identification of sensors
• Errors during assembly after engine repair

How to Fix

1. Connect the diagnostic scanner and read the error codes
2. Stop the engine and let it cool down
3. Find the location of the upstream oxygen sensors (sensors 1) on banks 1 and 2
4. Disconnect the electrical connectors of both sensors
5. Carefully unscrew the sensors from the exhaust manifold
6. Swap sensors - install bank 1 sensor in place, bank 2 sensor in place
7. Connect the correct electrical connectors to the appropriate sensors
8. Clear error codes using a scanner
9. Start the engine and check for errors
10. Carry out a test drive to confirm the problem has been resolved

Related codes

Error P0040 by Vehicle Brand