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Home >> Cadillac >> 1998 >> Catera >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0156 - Ho2S Circuit Bank 2, Sensor 2 >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  , then go to next step.
  2. Start and warm engine to normal operating temperature. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool remains less than 399 mV, go to step 4). If HO2S voltage value 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 P0156 is set, go to next step. If DTC P0156 is not set, see DIAGNOSTIC AIDS.
  4. Turn ignition on, with engine off. Disconnect HO2S connector. Check for signs of water or corrosion. Repair as necessary. If HO2S voltage value on scan tool is 375-525 mV, go to step 14). If HO2S 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 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, check voltage between ground and low circuit at HO2S 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 DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect the 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting the other sensors restores voltage to 700-800 mV, go to step 14). If disconnecting one of 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 connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S low circuit at ECM harness connector. If no voltage is present, go to next step. If voltage is present, go to step 15).
  9. Using DVOM, check harness continuity of HO2S 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 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 connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S 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 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 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. After replacing sensor, go to step 23).
  15. Repair short to voltage in HO2S low circuit. After repairs, go to step 23).
  16. Repair open or high resistance in HO2S low circuit. After repairs, go to step 23).
  17. Repair short to ground in HO2S low circuit. After repairs, go to step 23).
  18. Repair short to voltage in signal circuit. After repairs, go to step 23).
  19. Repair open or high resistance in signal circuit. After repairs, go to step 23).
  20. Repair short to ground in signal circuit. After repairs, go to step 23).
  21. Check for poor connections and terminal tension at ECM harness connector. 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 replacing ECM, 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 P0156 is set, go to step 2). If DTC P0156 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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