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Home >> Chevrolet >> 2001 >> Venture Base, Van Passenger >> Repair and Diagnosis (Single Page) >> Engine Performance >> Testing & Diagnosis >> Engine Controls Self-Diagnostics >> Diagnostic Tests >> DTC P0140: Heated Oxygen Sensor No. 2 Circuit Insufficient Activity ("A" & "B" Series) >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
  2. Using scan tool, reset fuel trim values. Start engine. Observe HO2S voltage on scan tool. If HO2S voltage is fixed within 412-500 millivolts, go to step  4. If HO2S voltage is not fixed within 412-500 millivolts, go to next step.
  3. Turn ignition off. The condition that set this DTC is not present. DTC may have been set by water intrusion in HO2S connector, intermittently open HO2S high signal circuit or low signal circuit, high resistance to ground in HO2S low signal and PCM ground circuits, inoperative HO2S heater, poor HO2S or PCM connector terminal contact, exhaust system leak, or a defective HO2S. Repair as necessary. After repairs, go to step  17. If no problem is found, condition is intermittent.
  4. Turn ignition off. Disconnect HO2S harness connector. Connect a jumper wire between a known-good ground and HO2S harness connector terminal "A" (Tan or Tan/White wire). See Figure or Figure . Connect a jumper wire between a known-good ground and HO2S harness connector terminal "B" (Purple or Purple/White wire). Turn ignition on, with engine off. Using scan tool, observe HO2S voltage. If voltage reading is less than 20 millivolts, go to step  7. If voltage reading is not less than 20 millivolts, go to next step.
  5. Turn ignition off. Remove jumper wires from HO2S terminals. Disconnect PCM harness connectors. Using a DVOM, check continuity of Purple or Purple/White wire between HO2S and PCM. Check continuity of Tan or Tan White wire between HO2S and PCM. If individual resistance of both circuits is less than 5 ohms, go to next step. If individual resistance of both circuits is not less than 5 ohms, go to step  9.
  6. Check for proper PCM connector terminal contact. Repair as necessary. After repairs, go to step  17. If connector terminal contacts are okay, go to step  16.
  7. Turn ignition off. Remove jumper wires HO2S terminals. Connect a test light between HO2S harness connector terminals "C" (Black or Black/White wire) and "D" (Pink wire). Start engine. If test light illuminates, go to next step. If test light does not illuminate, go to step  10.
  8. Turn ignition off. Reconnect HO2S harness connector. Disconnect PCM harness connectors. Using DVOM, check resistance between HO2S harness connector terminal "A" (Tan or Tan/White wire) and PCM harness connector C1 terminal No. 12 (Tan wire) or terminal No. 28 (Tan/White wire). See Figure. If resistance is less than 500 ohms, go to step  12. If resistance is not less than 500 ohms, go to step  11.
  9. Repair circuit with high resistance. After repairs, go to step  17.
  10. Turn ignition off. Repair open or high resistance in Pink wire, Black or Black/White wire between HO2S and PCM, or repair poor ground connection or an open heater fuse. If any of this problem was present, a DTC will be set. Diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . After repairs, go to step  17.
  11. Repair high resistance between Tan or Tan/white wire and PCM ground circuit. Problem can be caused by poor HO2S connector terminal contact, open sensor harness low signal circuit (requires HO2S replacement), sensor harness low signal circuit with high resistance (requires HO2S replacement) or a poor PCM ground connection. Problem could also be caused by a high PCM ground circuit resistance or an ungrounded exhaust system. After repairs, go to step  17.
  12. Check for exhaust system leaks upstream of suspect HO2S. The leak may be very small and will typically be within 12 inches of suspect HO2S. Repair as necessary. After repairs, go to step  17. If no problem is found, go to next step.
  13. Allow engine to cool to ambient temperature. Using DVOM, measure resistance between a PCM circuit ground terminal and PCM harness connector C1 terminal No. 12 (Tan wire) or terminal No. 28 (Tan/White wire). If resistance is 13 ohms, go to step  15. If resistance is not 13 ohms, go to next step.
  14. Remove HO2S and clean HO2S mounting threads. Apply anti-seize compound to sensor threads. Tighten HO2S to 30 ft. lbs. (41 N.m). Reconnect HO2S harness connector. Using DVOM, measure resistance a PCM circuit ground terminal and between PCM harness connector C1 terminal No. 12 (Tan wire) or terminal No. 28 (Tan/White wire). If resistance is less than 500 ohms, go to step  17. If resistance is not less than 500 ohms, go to next step.
  15. Replace HO2S 2. After replacing sensor, go to step  17.
  16. Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  17. Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Operate vehicle within conditions for running this DTC. See CODE ENABLE CRITERIA . If DTC runs and passes, go to next step. If DTC resets, go to step  2.
  18. Using scan tool, observe stored information and CAPTURE INFO. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  If no DTCs are displayed, system is okay.
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