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• When Monitored: • Set Condition: Possible Causes (K399) O2 SENSOR 2/2 HEATER CONTROL CIRCUIT SHORTED TO GROUND O2 SENSOR PCM Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - Diagnostic Test 1. O2 SENSOR HEATER OPERATION Turn the ignition off. NOTE: Wait a minimum of 8 minutes to allow the O2 Sensor to cool down before continuing the test. Allow 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? Yes >> Go To 2 No >> Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) 2. O2 HEATER ELEMENT Turn the ignition off. NOTE: Allow the O2 Sensor to cool down to room temperature. Measure the resistance across the O2 Sensor Heater element, between the O2 Heater Control terminal and the O2 NOTE: O2 Heater Element resistance values should be measured at 70°F (21.1°C). The resistance value will Is the O2 Sensor Heater Element resistance between 2.0 and 30.0 ohms? Yes >> Go To 3 No >> Replace the O2 Sensor. Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) 9 - 34 ENGINE ELECTRICAL DIAGNOSTICS KJ |