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Home >> Chevrolet >> 1996 >> Monte Carlo LS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 3.1L Engine >> Diagnostic Trouble Codes >> DTC P0140 - Ho2S Insufficient Activity Sensor 2 >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
  2. Ensure engine is at normal operating temperature. Start engine. Increase engine speed to 1200 RPM for 2 minutes. Observe HO2S voltage. If voltage is 400-500 mV, go to step 4). If voltage is not 400-500 mV, go to next step.
  3. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P0140 until DTC P0140 test runs. If scan tool indicates FAILED THIS IGN, go to next step. If scan tool does not indicate FAILED THIS IGN, see DIAGNOSTIC AIDS.
  4. Turn ignition on, with engine off. Disconnect HO2S 2 connector. Connect a jumper wire between ground and sensor signal circuit and ground circuit terminals at HO2S 2 harness connector. If voltage is less than 150 mV, go to step 8). If voltage is 150 mV or greater, go to next step.
  5. Remove jumper wire. Using DVOM, measure voltage between signal circuit and heater ground circuit terminals at HO2S 2 harness connector. 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 connector. Check continuity of HO2S 2 ground circuit between PCM and HO2S 2 connector. If resistance is less than 5 ohms, go to step 9). If resistance is 5 ohms or greater, repair open circuit. After repair is completed, go to step 13).
  7. Turn ignition off. Disconnect PCM connector. Check continuity of HO2S 2 signal circuit between PCM and HO2S 2 connector. If resistance is less than 5 ohms, go to step 10). If resistance is 5 ohms or greater, repair open circuit. After repair is completed, go to step 13).
  8. Check for poor HO2S 2 signal or ground circuit terminal connection at HO2S 2 connector. Repair as necessary. After repair is completed, go to step 13). If connection is okay, go to step 11).
  9. Check for poor HO2S 2 ground circuit terminal connection at PCM connector. Repair as necessary. After repair is completed, go to step 13). If connection is okay, go to step 12).
  10. Check for poor HO2S 2 signal circuit terminal connection at PCM connector. Repair as necessary. After repair is completed, go to step 13). If connection is okay, go to step 12).
  11. Replace HO2S 2. After repair is completed, go to step 13).
  12. Replace PCM. Program replacement PCM using required equipment. After repairs, go to next step.
  13. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P0140 until DTC P0140 test runs. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.
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