312002999 - P0657 Congruence of main relay battery voltage upstream/downstream

The error is detected if the voltage acquired from the control unit downstream of the main relay is greater than (with detail voltage above threshold) or less than (with detail voltage below threshold) the two calibrated levels
Test results
1RELAY POWER SUPPLY CHECKAll OKProblems encounteredOperation
Check there are no faults in the main relay supply circuit by performing theSee Test 1060GL CHECK ON OPERATION OF ENGINE MANAGEMENT CONTROL UNIT MAIN RELAYEnd of diagnosis--