Common check engine codes for Volvo vehicles include P0420, P0421 and P0430, which indicate a catalytic converter failure, and P0171 and P0174, which indicate a problem with the mass air flow sensors that measure the amount of air taken into the engine. Vacuum leaks may also cause these codes.
Some other common Volvo check engine codes are P0130, P0133, P0134, P0135 and P0136. These codes indicate a failure of the oxygen sensor, which monitors the ratio of air to fuel used by the engine. They may also indicate a short circuit in the sensor’s wiring. Codes P0400 and P0401 indicate a clog or a valve that is stuck in the Exhaust Gas Recirculation system. The accumulation of carbon deposits and exhaust debris is generally the cause behind these codes.