For a complete wiring diagram Refer to Section 8W.When Monitored:Ignition on.Set Condition:When the PCM recognizes the Auxiliary 5-volt Supply circuit voltage is varying too much to quickly. One Trip Fault. ETC light is flashing.Possible Causes(F856) AUXILIARY 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND(F856) AUXILIARY 5-VOLT SUPPLY CIRCUIT SHORTED TO BATTERY VOLTAGE(F856) AUXILIARY 5-VOLT SUPPLY CIRCUIT OPEN5-VOLT SENSORPCMAlways perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).1. 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. (F856) AUXILIARY 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND

Turn the ignition off.Disconnect the C1 PCM harness connector.Disconnect all the Sensors that share the (F856) Auxiliary 5-volt Supply circuit.This code can be caused by the improper installation of after market accessories that may be causing excessive noise on the (F856) 5-volt Supply circuit.Measure the resistance between ground and the (F856) Auxiliary 5-volt Supply circuit at the CMP Sensor harness connector.Is the resistance below 100 ohms?YesRepair the short to ground in the (F856) Auxiliary 5-volt Supply circuit.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) NoGo To 33. SENSOR SHORTED TO GROUND

Connect the C1 PCM harness connector and all the previously disconnected Sensors except for the CMP Sensor harness connector.Ignition on, engine not running.Measure the voltage on the (F856) Auxiliary 5-volt Supply circuit in the CMP Sensor harness connector.You must Turn the Ignition OFF when disconnecting any of the Sensor harness connectors and Turn the Ignition On to check the voltage readings.While monitoring the voltage, disconnect each Sensor harness connector that shares the (F856) Auxiliary 5-volt Supply circuit, one at a time.Does the voltage increase above 4.5 volts when disconnecting any of the Sensor harness connectors?YesReplace the Sensor that causes the (F856) Auxiliary 5-volt Supply circuit voltage to increase when disconnected.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) NoGo To 44. 5-VOLT SENSOR

Turn the ignition off.Connect all the previously disconnected Sensors except for the CMP Sensor harness connector.Ignition on, engine not running.Measure the voltage on the (F856) Auxiliary 5-volt Supply circuit in the CMP Sensor harness connector.Is the voltage below 4.5 volts?YesGo To 5NoReplace the Cam Position Sensor.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) 5. (F856) AUXILIARY 5-VOLT SUPPLY CIRCUIT SHORTED TO BATTERY VOLTAGE

Turn the ignition off.Disconnect the C1 PCM harness connector.Disconnect all the Sensors that share the (F856) Auxiliary 5-volt Supply circuit.Ignition on, engine not running.Measure the voltage on the (F856) Auxiliary 5-volt Supply circuit at the CMP Sensor harness connector.Is the voltage above 0 volts?YesRepair the short to battery voltage in the (F856) Auxiliary 5-volt Supply circuit.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) NoGo To 66. (F856) AUXILIARY 5-VOLT SUPPLY CIRCUIT OPEN

Turn the ignition off.Reconnect all the sensors that were disconnected in the previous step except the CMP Sensor harness connector.Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.Measure the resistance in the (F856) Auxiliary 5-volt Supply circuit from the Sensor harness connector to the appropriate terminal of special tool #8815.It may be necessary to perform this test from every sensor that uses the (F856) Auxiliary 5-volt Supply circuit.Is the resistance below 5.0 ohms?YesGo To 7NoRepair the open in the (F856) Auxiliary 5-volt Supply circuit.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) 7. 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)