P0401 - Exhaust Gas Recirculation Flow Insufficient Detected.
The main function of the EGR is to allow some exhaust gas into the intake system, which lowers the exhaust temperature and reduces the formation of SOx's and NOx's, pollutants that are known to cause acid rain. Cars ran for decades without the EGR, and, if you have a bad head gasket, then the EGR function is the least of your worries. With a 12 year old clunker of a car like yours, worry about that head gasket first. That will kill the engine faster than the unplugged EGR.