2003 Volvo S40 Codes P0456 and P0139

Hi HM,

Thank you for the donation.

P0456 EVAP Leak Monitor Small Leak Detected.
This usually is caused by a faulty gas cap or it has not been closed correctly.

Remove gas cap and check the seals for wear or improper seating. When closing gas cap, it must at least click 3 times when tightening it.
Some running might be required before the DTC clears up.

P0139 Oxygen Sensor Circuit Slow Response. This could be due to a faulty O2 sensor or its wiring circuit. Testings would be required to confirm if it is the unit or wiring circuits.