For a complete wiring diagram Refer to Section 8WWhen Monitored:With the ignition on and the Oxygen Sensor Heater command on.Set Condition:The ECM detects an implausible voltage on the (K79) O2 1/1 Heater Control circuit for 2.0 seconds.Possible CausesINTERMITTENT DTC(K79) O2 1/1 HEATER CONTROL CIRCUIT SHORTED TO VOLTAGE(K79) O2 1/1 HEATER CONTROL CIRCUIT SHORTED TO GROUND(K79) O2 1/1 HEATER CONTROL CIRCUIT OPEN OR HIGH RESISTANCE(F344) FUSED ASD RELAY OUTPUT 2 CIRCUIT OPEN OR HIGH RESISTANCEOXYGEN SENSORENGINE CONTROL MODULE (ECM)Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)1. DTC IS ACTIVEIgnition on, engine not running.With the scan tool, Clear DTCs in the Engine Control Module (ECM).With the scan tool, actuate the Oxygen Sensor Heater.Monitor the scan tool for at least two minutes.With the scan tool, select View DTCs.Is the status Active for this DTC?YesGo To 2 NoRefer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure.(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)2. (K79) O2 1/1 HEATER CONTROL CIRCUIT SHORTED TO VOLTAGE

Turn the ignition off.Disconnect the Oxygen Sensor harness connector.Disconnect the Engine Control Module (ECM) harness connector.Remove the ASD Relay from theTIPM.Connect a jumper wire between cavity 30 and cavity 87 of the ASD Relay Connector.Turn the ignition on.Measure the voltage of the (K79) O2 1/1 Heater Control circuit in the Oxygen Sensor harness connector.Is there any voltage present?YesRepair the (K79) O2 1/1 Heater Control circuit for a short to voltage.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo to 33. (K79) O2 1/1 HEATER CONTROL CIRCUIT SHORTED TO GROUND

Turn the ignition off.Remove the jumper wire and install the ASD Relay..Measure the resistance between ground and the (K79) O2 1/1 Heater Control circuit in the Oxygen Sensor harness connector.Is the resistance above 1000 ohms?YesGo to 4NoRepair the (K79) O2 1/1 Heater Control circuit for a short to ground.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)4. (K79) O2 1/1 HEATER CONTROL CIRCUIT OPEN OR HIGH RESISTANCE

Measure the resistance of the (K79) O2 1/1 Heater Control circuit between the Oxygen Sensor harness connector and the Engine Control Module (ECM) harness connector.Is the resistance below 10.0 ohms?YesGo to 5NoRepair the (K79) O2 1/1 Heater Control circuit for an open circuit or high resistance.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)5. (F344) FUSED ASD RELAY OUTPUT 2 CIRCUIT OPEN OR HIGH RESISTANCE

Measure the resistance of the (F344) Fused ASD Relay Output 2 circuit between the Oxygen Sensor harness connector and the ASD Relay connector.Is the resistance below 10.0 ohms?YesGo to 6NoRepair the (F344) Fused ASD Relay Output 2 circuit for an open circuit or high resistance.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)6. OXYGEN SENSORConnect the Engine Control Module (ECM) harness connector.Replace the Oxygen Sensor in accordance with the Service Information.Start the engine.Allow the engine to reach normal operating temperature.Monitor the scan tool for at least two minutes.With the scan tool, select View DTCs.Is the status Active for this DTC?YesGo to 7NoTest Complete.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)7. ENGINE CONTROL MODULE (ECM)Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Oxygen Sensor and the Engine Control Module (ECM).Look for any chafed, pierced, pinched, or partially broken wires.Look for broken, bent, pushed out or corroded terminals.Refer to any Technical Service Bulletins that may apply.Were any problems found?YesRepair as necessary.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoReplace the Engine Control Module (ECM) in accordance with the Service Information.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)