Common diagnostic codes for Volvos that cause the Check Engine light to come fully on or blink include emissions-related codes, codes indicating fuel injector malfunction, codes indicating cylinder misfire or knocking, and codes indicating ignition coil or electronic control module malfunction or failure. The most common reason for a check engine light to come on is an unusual reading from the oxygen sensors, and a vehicle will not pass state emissions inspection until the problem is resolved.
Code numbers that indicate an unusual reading from the oxygen sensors include all codes including or between P0030 and P0058 and between P0130 and P0161. A faulty signal is usually the sign of a failing oxygen sensor, while a reading of too low or high suggests problems within the engine. Codes between P0201 and P0206 and between P0261 and P0277 indicate an unusual reading from a fuel injector. Codes between P0300 and P0306 indicate cylinder misfires, usually a sign of an ignition or fuel delivery problem. If a problem causing a misfire code also gets a code between P0351 and P0355 or P2300 to P2313, the source of a problem is likely a malfunctioning ignition coil.
When you plug in your vehicle to a diagnostic machine, pay attention to the code's description, as it indicates whether the unusual signal is permanent or intermittent and whether the reading is too low, too high or faulty. For an intermittent code result, reset the electronic control module by disconnecting the negative battery cable, and determine if the check engine light returns before continuing troubleshooting.