Mercury Optimax Diagnostic Guide., Page 11Get this manual
OPTIMAX DIAGNOSTIC GUIDE
Procedure 8
MAIN POWER RELAY FAULT
Typically the starter will draw 210 amps under the load of cranking the engine, lowering the voltage available from the batteryIf the battery voltage available from the battery is less than volts during cranking, the Main Power Relay (MPR) may not close or even remain closed during cranking, resulting in no spark, no injector activity or no voltage to the electric fuel pumpUnder these conditions the ECM concludes that the MPR output circuit is at fault and sets code, which is stored in the Freeze Frame bufferThere are seldom failures with the MPRClose examination of the MPR Freeze Frame buffer will probably indicate very low battery voltage condition when the fault was recordedThe higher the frequency count, the more likely that the battery voltage is low
Procedure 9