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Home >> Oldsmobile >> 2003 >> Bravada AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Self-Diagnostics - 4.2L >> Diagnostic Tests >> DTC P1137: Ho2S Circuit - Lean System (Bank 1; Sensor 2) >> Diagnostic Procedures

Diagnostic Procedures

  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Operate engine at normal operating temperature. Operate engine at greater than 1200 RPM for 2 minutes. Observe the HO2S 2 voltage parameter with the scan tool. Does the scan tool indicate that the HO2S 2 voltage is less than 399 mV? If yes, go to step  4. If no, go to next step.
  3. Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions For Running the DTC. See CONDITIONS FOR RUNNING DTC . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to next step. If no, problem is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER EXT article.
  4. Turn ignition off. Disconnect the HO2S 2 sensor. Turn ignition on, with engine off. Measure the voltage of the HO2S 2 high signal circuit on the PCM side with the DVOM. Does the voltage measure within 350-550 mV? If yes, go to step  6. If no, go to next step.
  5. Test the HO2S 2 high signal circuit for a short to ground or a short to the low signal circuit. Did you find and correct the condition? If yes, go to step  11. If no, go to step  8.
  6. The HO2S 2 may be detecting a lean exhaust condition. Inspect HO2S connector for water intrusion, exhaust leak between HO2S 2 and engine, incorrect fuel pressure, lean fuel injectors, or inaccurate MAF sensor. Repair as necessary. Did you find and correct the condition? If yes, go to step  11. If no, go to next step.
  7. Inspect for poor connections at the harness connector of the HO2S 2 sensor. Did you find and correct the condition? If yes, go to step  11. If no, go to step  9.
  8. Inspect for poor connections at the PCM harness connector. Did you find and correct the condition? If yes, go to step  11. If no, go to step  10.
  9. Replace HO2S 2. After replacing sensor, go to step  11.
  10. Replace PCM. See REMOVAL & INSTALLATION - BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER EXT article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  11. Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running the DTC. See CONDITIONS FOR RUNNING DTC . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to step  2. If no, go to next step.
  12. Observe the stored information, Capture Info with scan tool. Does scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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