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Theory of Operation The State of Change (SOC) catalyst monitor uses the signals from both the upstream and downstream O2 sensors • When Monitored: • Set Condition: Possible Causes EXHAUST LEAK ENGINE MECHANICAL CONDITION AGING O2 SENSOR CATALYTIC CONVERTER Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - Diagnostic Test 1. ACTIVE DTC NOTE: A new rear O2 Sensor along with an aging front O2 Sensor may cause the DTC to set. Review the NOTE: If an O2 Sensor DTC set along with the Catalytic Converter Efficiency DTC diagnose the O2 Sensor NOTE: Check for contaminants that may have damaged the O2 Sensor and Catalytic Converter: contami- With a scan tool, read DTCs. Is the DTC active at this time? Yes >> Go To 2 No >> Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) 2. VISUALLY INSPECT CATALYTIC CONVERTER Inspect the Catalytic Converter for the following damage. Damage Catalytic Converter, dents or holes. Severe discoloration caused by overheating the Catalytic Converter. Catalytic Converter broke internally. Inspect both ends of the converter, inlet and outlet. Leaking Catalytic Converter. Were any problems found? Yes >> Replace the Catalytic Converter. Repair the condition that may have caused the failure. Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) No >> Go To 3 9 - 330 ENGINE ELECTRICAL DIAGNOSTICS KJ |