P0643-PRIMARY 5-VOLT SUPPLY CIRCUIT HIGHFor a complete wiring diagram Refer to Section 8W.When Monitored:Ignition on.Set Condition:When the PCM recognizes the Primary 5-volt Supply circuit voltage is too high. One Trip Fault. ETC light is flashing.
Possible Causes(F855) PRIMARY 5-VOLT SUPPLY SHORTED TO BATTERY VOLTAGEPCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).Diagnostic Test1.ACTIVE DTCIgnition on, engine not running.With a scan tool, select View DTCs.Is the DTC Active at this time?YesGo To 2NoRefer to the INTERMITTENT CONDITION Diagnostic Procedure.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)2.(F855) PRIMARY 5-VOLT SUPPLY SHORTED TO BATTERY VOLTAGETurn the ignition off.Disconnect the C2 PCM harness connector.Disconnect all the Sensors that share the (F855) Primary 5-volt Supply circuit.Improperly installed aftermarket accessories can cause this DTC to set. Check for wiring added by customer.Ignition on, engine not running.Measure the voltage on the (F855) Primary 5-volt Supply circuit at the CKP Sensor harness connector.Is the voltage above 5.2 volts?YesRepair the short to battery voltage in the (F855) Primary 5-volt Supply circuit.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 33.PCMBefore continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.Were there any problems found?YesRepair as necessary.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoReplace and program the Powertrain Control Module per Service Information.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)