For a complete wiring diagram Refer to Section 8W.When Monitored:Battery voltage above 10.6 volts, ASD is powered up, and O2 heater is on.Set Condition:Desired state does not match Actual state. One Trip Fault. Three good trips to turn off the MIL.Possible Causes(K399) O2 SENSOR 2/2 HEATER CONTROL CIRCUIT SHORTED TO GROUNDO2 SENSOR PCMAlways perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).1. O2 SENSOR HEATER OPERATIONTurn the ignition off.Wait a minimum of 8 minutes to allow the O2 Sensor to cool down before continuing the test. Allow the O2 Sensor voltage to stabilize at 5.0 volts.Ignition on, engine not running.With a scan tool, actuate the O2 Heater Test.With the scan tool, monitor 2/2 O2 Sensor voltage for at least 2 minutes.Does the O2 Sensor voltage stay above 4.5 volts?YesGo To 2NoRefer to the INTERMITTENT CONDITION Diagnostic Procedure.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) 2. O2 HEATER ELEMENTTurn the ignition off.Allow the O2 Sensor to cool down to room temperature.Disconnect the 2/2 O2 Sensor harness connector.Measure the resistance across the O2 Sensor Heater element, between the O2 Heater Control terminal and the O2 Heater ground terminal in the component connector.O2 Heater Element resistance values should be measured at 21.1° C (70° F). The resistance value will vary with different temperature values.Is the O2 Sensor Heater Element resistance between 2.0 and 30.0 ohms?YesGo To 3NoReplace the O2 Sensor.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) 3. O2 SENSOR

Ignition on, engine not running.Using a 12-volt test light connected to ground, probe the (K399) O2 2/2 Heater Control circuit in the O2 Sensor harness connector.Make sure the test light is probing the circuit before actuating the Heater Test or a DTC may set and not allow the actuation.With a scan tool, actuate the O2 Heater Test with the O2 Sensor harness connector still disconnected.Does the test light illuminate brightly and flash on and off during the actuation?YesReplace the O2 Sensor.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) NoGo To 44. (K399) O2 2/2 HEATER CONTROL CIRCUIT SHORTED TO GROUND

Turn the ignition off.Disconnect the C3 PCM harness connector.Measure the resistance between ground and the (K399) O2 2/2 Heater Control circuit in the O2 Sensor harness connector.Is the resistance below 5.0 ohms?YesRepair the short to ground in the (K399) O2 2/2 Sensor Heater Control circuit.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) NoGo To 55. 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)