Often when problems with the charging system are being investigated, the alternator is not the problem. If a low battery condition is present, test the batteries first. See Special Instruction, SEHS7633, “Battery Test Procedure” for more information. If the engine cranks slowly, then test the starting system. See Service Magazine, SEPD0020, “Testing The Starter On The Engine” for more information. If a warning indicator for the charging system is ON, see Service Magazine, SEBD1751, “Difference Between Alternator Indicator In Electronic Monitoring System (EMS) And Low Voltage Indicator In Operating Monitoring System (OMS)”. When a problem with the charging system is suspected, then complete the testing that is described in Diagnostic Function, “Charging System”.