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Home >> GMC >> 1999 >> Forward Control 6.5 F, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes - DTC P0135-P0204 >> DTC P0136 >> DTC P0136: Ho2S Circuit-Bank 1, Sensor 2 (3.0L "V" Body) >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step.
  2. Start engine and run to normal operating temperature. Using scan tool, monitor HO2S 2 voltage. If HO2S 2 voltage on scan tool remains less than 399 mV, go to step  4. If HO2S 2 voltage on scan tool does not remain less than 399 mV, go to next step.
  3. Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0136 is set, go to next step. If DTC P0136 is not set, see DIAGNOSTIC AIDS .
  4. Turn ignition on, with engine off. Disconnect HO2S 2 connector. Check for signs of water or corrosion. Repair as necessary. If HO2S 2 voltage value on scan tool is 375-525 mV, go to step  14. If HO2S 2 voltage value on scan tool is not 375-525 mV, go to next step.
  5. Using DVOM, measure voltage between ground and signal circuit at HO2S 2 harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step  11.
  6. Using DVOM, measure voltage between ground and low circuit at HO2S 2 harness connector. If voltage is 700-800 mV, go to step  22. If voltage is not 700-800 mV, go to next step.
  7. Continue to monitor voltage from HO2S 2 low circuit between harness connector and ground. Disconnect 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting one of the other sensors restores voltage to 700-800 mV, go to step  14. If disconnecting the other sensors does not restore voltage to 700-800 mV, go to next step.
  8. Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connectors located in engine compartment relay center. Turn ignition on. Using DVOM, measure voltage between ground and HO2S 2 low circuit at ECM harness connector. If any voltage is present, go to step  15. If no voltage is present, go to next step.
  9. Using DVOM, check harness continuity of HO2S 2 low circuit. If continuity is present, go to next step. If continuity is not present, go to step  16.
  10. Using DVOM, check harness continuity between HO2S 2 low circuit and ground. If continuity is present, go to step  17. If continuity is not present, go to step  21.
  11. Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connectors located in engine compartment relay center. Turn ignition on. Using DVOM, measure voltage between ground and HO2S 2 signal circuit at ECM harness connector. If any voltage is present, go to step  18. If no voltage is present, go to next step.
  12. Using DVOM, check harness continuity of HO2S 2 signal circuit. If continuity is present, go to next step. If continuity is not present, go to step  19.
  13. Using DVOM, check harness continuity between HO2S 2 signal circuit and ground. If continuity is present, go to step  20. If continuity is not present, go to step  21.
  14. Replace shorted HO2S 2. After repairs, go to step  23.
  15. Repair short to voltage in HO2S 2 low circuit. After repairs, go to step  23.
  16. Repair open or high resistance in HO2S 2 low circuit. After repairs, go to step  23.
  17. Repair short to ground in HO2S 2 low circuit. After repairs, go to step  23.
  18. Repair short to voltage in HO2S 2 signal circuit. After repairs, go to step  23.
  19. Repair open or high resistance in HO2S 2 signal circuit. After repairs, go to step  23.
  20. Repair short to ground in HO2S 2 signal circuit. After repairs, go to step  23.
  21. Check for poor connections and terminal tension at ECM harness connectors. Repair as necessary. After repairs, go to step  23. If connections and terminals are okay, go to next step.
  22. Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After repairs, go to next step.
  23. Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0136 is set, go to step  2. If DTC P0136 is not set, go to next step.
  24. If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.
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