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Home >> Oldsmobile >> 1998 >> Regency >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control Systems Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0140 - Ho2S 2 Insufficient Activity >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Start and warm engine to normal operating temperature. Place transmission in Park or Neutral. Apply parking brake. Increase engine speed to greater than 1200 RPM for 2 minutes. Using scan tool, monitor HO2S 2 voltage. If displayed voltage is not switching from greater than 475 mV to less than 425 mV, go to next step. If voltage is switching as specified, go to step 4).
  3. Turn engine off. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS data. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0140 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0140 FAILED THIS IGN, see DIAGNOSTIC AIDS.
  4. Disconnect HO2S 2 harness connector. Connect a jumper wire between HO2S 2 harness connector signal and ground circuits, and chassis ground. If voltage is less than 150 mV, go to step 8). If voltage is not less than 150 mV, go to next step.
  5. Remove jumper wire. Using DVOM, check voltage between HO2S 2 harness connector signal and heater ground circuits. If voltage is about 450 mV, go to next step. If voltage is not about 450 mV, go to step 7).
  6. Turn ignition off. Disconnect PCM harness connectors. Check resistance of HO2S 2 harness connector ground circuit. If resistance is greater than 5 ohms, repair open or faulty connection. After repairs, go to step 13). If resistance is not greater than 5 ohms, go to step 9).
  7. Turn ignition off. Disconnect PCM connectors. Check resistance of HO2S 2 harness connector signal circuit. If resistance is greater than 5 ohms, repair open or faulty connection as necessary. After repairs, go to step 13). If resistance is not greater than 5 ohms, go to step 10).
  8. Check for faulty connection at HO2S 2. Repair as necessary. After repairs, go to step 13). If connection is okay, go to step 11).
  9. Check for faulty connection at PCM. Repair as necessary. After repairs, go to step 13). If connection is okay, go to step 12).
  10. Check for faulty connection at PCM. Repair as necessary. After repairs, go to step 13). If connection is okay, go to step 12).
  11. Replace HO2S No. 2. After replacing sensor, go to step 13).
  12. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  13. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P0140. If scan tool displays DTC P0140 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P0140 FAILED THIS IGN, repair is complete.
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