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P0139-O2 SENSOR 1/2 SLOW RESPONSE (CONTINUED) For the Engine circuit diagram (Refer to 9 - ENGINE - SCHEMATICS AND DIAGRAMS). For a complete wiring diagram Refer to Section 8W. Theory of Operation The downstream O2 Sensor is located in the exhaust path behind the catalytic converter, is monitored for proper • When Monitored: • Set Condition: Possible Causes EXHAUST LEAK (K141) O2 1/2 SIGNAL CIRCUIT (K904) O2 RETURN DOWNSTREAM CIRCUIT O2 SENSOR Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - Diagnostic Test 1. ACTIVE DTC NOTE: Check for contaminants that may have damaged the O2 Sensor: contaminated fuel, unapproved sil- NOTE: After the repairs have been made, verify proper O2 Sensor operation. If all the O2 Sensor voltage 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. EXHAUST LEAK Start the engine. Inspect the exhaust system for leaks between the engine and the O2 Sensors. Are there any exhaust leaks? Yes >> Repair or replace the leaking exhaust parts as necessary. Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) No >> Go To 3 HB ENGINE ELECTRICAL DIAGNOSTICS 9 - 187 |