More than likely, yes, trouble code P1500 will cause your Mitsubishi Galant to fail the smog check. P1500 indicates that either your Galant's alternator has a fault or that a connection to the alternator harness is open or shorted. Although the check light is not on, this trouble code indicates there is an electrical problem with the alternator which might cause your Mitsubishi's engine & emissions control computer to receive voltage levels below required parameters; which might then effect emission sensor input and/or output voltages.
