Code 78 (GS300 & SC300)

Condition is: engine speed less than 1000 RPM, open or short in fuel pump circuit for more than one second, open in input circuit of fuel pump ECM or open/short in diagnostic signal line (DI) of fuel pump ECM. Probable cause: open or short in fuel pump ECM circuit, defective fuel pump ECM, fuel pump, faulty ECM power source circuit or defective ECM.