+18 2004 Mercury Grand Marquis Ls Check Engine Light Codes References. Follow scan tool manufacturer's operating instructions to access the diagnostic trouble codes (dtc's). There will always be trouble codes associated with the mercury grand marquis’s check engine light flashing.
The scanner will show the engine fault code that the computer has detected, which is related to a certain problem that is affecting the engine. A code scanner is cheap. P0442 is a universal obd ii diagnostic trouble code, applicable across vehicle manufacturers.
