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Theory of Operation This diagnostic provides a continuous check of the O2 heater circuit during operation. The heater circuit is momen- • When Monitored: • Set Condition: Possible Causes (K299) O2 1/2 HEATER CONTROL CIRCUIT OPEN (Z42) O2 HEATER GROUND CIRCUIT OPEN O2 SENSOR HEATER ELEMENT 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 1/2 O2 Sensor voltage for at least 2 minutes. Does the 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 SENSOR HEATER ELEMENT Turn the ignition off. NOTE: Allow the O2 sensor to cool down to room temperature. Measure the resistance of the O2 Heater Element across the O2 Sensor connector between the O2 Heater Control NOTE: O2 Heater Element resistance values should be measured at 70°F (21.1°C). The resistance value will Is the resistance of the O2 Sensor Heater Element 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 - 150 ENGINE ELECTRICAL DIAGNOSTICS KJ |