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Home >> Chevrolet >> 2001 >> Venture Base, Van Passenger >> Repair and Diagnosis >> External Pages >> Different car >> Section 68 (Engine Control System Self-Diagnostics - 3.8L) >> Diagnostic Tests >> DTC P0140: Ho2S Circuit Insufficient Activity - Sensor 2 (Regal) >> Diagnostic Procedures

Diagnostic Procedures

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  1. Perform Diagnostic System Check - Engine Controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing Diagnostic System Check - Engine Controls, go to next step.
  2. Ensure that the engine is at the operating temperature. Operate the engine above 1200 RPM for 2 minutes while monitoring the HO2S 2 voltage on the scan tool. Does the voltage vary outside 425-475 millivolts? If yes, go to next step. If no, go to step  4.
  3. Turn on the ignition, with the engine off. Review and record scan tool Failure Records data. Operate the vehicle within Failure Records conditions. Using a scan tool, observe the Specific DTC info for DTC P0140 until the DTC P0140 test runs. Does the DTC reset? If yes, go to next step. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  4. Turn on the ignition, with the engine off. Disconnect the HO2S 2, and jumper the HO2S high signal and low signal circuits on the PCM side to ground. With a scan tool, observe the HO2S 2 voltage. Does the voltage measure less than 150 millivolts? If yes, go to step  8. If no, go to next step.
  5. Remove the jumper wire from the HO2S high signal circuit, and leave the HO2S low signal circuit jumpered to ground. Using a DMM, measure the voltage between the HO2S 2 high signal circuit on the PCM side and the HO2S 2 heater ground circuit. Does the voltage measure near 4.5 volts? If yes, go to next step. If no, go to step  7.
  6. Turn off the ignition. Disconnect the PCM. Check the continuity of the HO2S 2 low signal circuit. If the HO2S 2 low circuit measures more than 5 ohms, repair the open or poor connection as necessary. Did you find and correct the condition? If yes, go to step  13. If no, go to step  9.
  7. Turn off the ignition. Disconnect the PCM. Check the continuity of the HO2S 2 high signal circuit between the PCM harness connector and the HO2S 2 harness connector. If the HO2S 2 high signal circuit measures more than 5 ohms, repair the open or poor connection as necessary. Did you find and correct the condition? If yes, go to step  13. If no, go to step  10.
  8. Inspect the HO2S 2 high signal circuit or the low signal circuit for a poor connection at the HO2S 2 harness connector. If a condition is found, repair the circuit as necessary. Did you find and correct the condition? If yes, go to step  13. If no, go to step  11.
  9. Inspect the HO2S 2 low signal circuit for a poor connection at the PCM. If a condition is found, repair the condition as necessary. Did you find and correct the condition? If yes, go to step  13. If no, go to step  12.
  10. Inspect the HO2S 2 high signal circuit for a poor connection at the PCM. If a condition is found, repair the condition as necessary. Did you find and correct the condition? If yes, go to step  13. If no, go to step  12.
  11. Replace HO2S 2. After repairs, go to step  13.
  12. Replace PCM. Program replacement PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  13. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within Conditions for Running DTC. Does DTC run and pass? If yes, go to next step. If no, go to step  2.
  14. Using scan tool, observe stored information. Does scan tool displays any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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