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Diagnosis & Repair Procedure

NOTE: For better performance and results of this diagnostic procedure, usage of appropriate wiring diagram is recommended. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
NOTE: Perform all voltage and resistance tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use an ohmmeter to isolate wiring harness shorts or opens.
  1. If engine system check has been performed, go to next step. If engine system check has not been performed, perform TEST D: ENGINE SYSTEM CHECK  under SYSTEM TESTS, then go to next step.
  2. If on DTC confirmation test procedure any DTC other than fuel system (P0171 or P0172) and HO2S-1 (P0134) were retrieved, perform appropriate diagnose test procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no other DTCs are retrieved, go to next step.
  3. Start engine and allow it to reach normal operating temperature. Increase engine speed to 2000 RPM for 60 seconds and release accelerator pedal. Repeat process 5 or 6 times. Using scan tool, observe HO2S-2 values. If HO2S-2 voltage does not deflect from more than 0.35 volt to less than 0.25 volt, go to next step. If HO2S-2 voltage deflect from over 0.35 volt to under 0.25 volt, check fuel system referring to DTC P0171 OR DTC P0172 . After repair, repeat DTC CONFIRMATION TEST .
  4. Turn ignition switch to LOCK position. Disconnect HO2S-2 4-pin harness connector C50. See Figure. Check HO2S-2 and harness connector terminals for corrosion or poor connection. If connector terminals are faulty, repair as necessary and repeat DTC CONFIRMATION TEST . If connector terminals are okay, check for continuity between ground and HO2S-2 harness connector C50 terminal No. 1 (Orange wire). See Figure. If continuity is found, go to next step. If continuity is not found, check ECM ground circuits (Black/Orange wire) and (Black wire) for open or short between ECM and ground. If ground circuits are faulty, repair as necessary and repeat DTC CONFIRMATION TEST . If ground circuits are okay, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST .
  5. Turn ignition switch to ON position. Measure voltage between ground and HO2S-2 harness connector terminal No. 1 (Orange wire). See Figure. If voltage is 0.1 volt or less, go to next step. If voltage is more than 0.1 volt, check for short circuit in Orange wire between HO2S-2 and ECM. If short circuit is found, repair as necessary and repeat DTC CONFIRMATION TEST . If short circuit is not found, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST .
  6. Turn ignition switch to LOCK position. Disconnect ECM harness connector C45. See Figure. Measure resistance between ECM harness connector C45 terminals No. 11 and HO2S-2 harness connector C50 terminal No. 2 (White wire). See Figure and Figure . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, check White wire for open or short circuit between HO2S-2 and ECM. If open or short circuit is found, repair as necessary and repeat DTC CONFIRMATION TEST . If open or short circuit is not found, check ECM ground circuits (Black/Orange wire) and (Black wire) for open or short between ECM and ground. If ground circuits are faulty, repair as necessary and repeat DTC CONFIRMATION TEST . If ground circuits are okay, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST .
  7. Measure resistance between ground and HO2S-2 harness connector C50 terminal No. 2 (White wire). See Figure. If resistance is infinity, go to next step. If any resistance is found, repair short to ground in White wire between HO2S-2 and ECM. After repair, repeat DTC CONFIRMATION TEST .
  8. Turn ignition switch to ON position. Measure voltage between ground and HO2S-2 harness connector C50 terminal No. 2 (White wire). See Figure. If voltage is zero volt, go to next step. If any voltage is found, repair short to voltage in White wire between HO2S-2 and ECM. After repair, repeat DTC CONFIRMATION TEST .
  9. Turn ignition switch to LOCK position. Check HO2S-2 performance referring to DTC P0141: HEATED OXYGEN SENSOR NO. 2 - HEATER CIRCUIT MALFUNCTION . If diagnostic results are okay, go to next step. If diagnostic results are faulty, repair as necessary and repeat DTC CONFIRMATION TEST .
  10. Start engine and check exhaust system for leaks. If any exhaust leak is found, repair as necessary and repeat DTC CONFIRMATION TEST . If no exhaust leaks are found, perform fuel pressure check. See FUEL PRESSURE under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. If fuel pressure is okay, go to next step. If fuel pressure is faulty, repair as necessary and repeat DTC CONFIRMATION TEST .
  11. Check throttle body for clog, leak or damage. If throttle body is faulty, repair or replace as necessary. See THROTTLE BODY under AIR INDUCTION SYSTEMS in REMOVAL & INSTALLATION article. After repair, repeat DTC CONFIRMATION TEST . If throttle body is okay, perform HO2S-2 component test, see HEATED OXYGEN SENSOR NO. 2 under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article. If HO2S-2 is faulty, replace as necessary, see HEATED OXYGEN SENSORS NO. 1 & 2 under ENGINE SENSORS & SWITCHES in REMOVAL & INSTALLATION article. If HO2S-2 is okay, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST .
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