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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 81 (Engine Controls - Self-Diagnostics - 4.8L, 5.3L & 6.0L) >> Diagnostic Tests >> DTC P0140 & P0160: Ho2S Circuit - Insufficient Activity - Bank 1 & 2, Sensor 2 (W/Isolated Ground) >> Diagnostic Procedures

Diagnostic Procedures

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  1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
    2. NOTE: Allow the engine to cool for one-half hour before proceeding with this diagnostic. This allows the HO2S signal voltage to return to bias voltage, approximately 447 mV.
  2. Install a scan tool. Turn ON the ignition, with the engine OFF. Immediately observe the affected HO2S voltage for 2 minutes. Does the HO2S voltage go from bias voltage to more than or less than 300-600 mV? If yes, go to next step. If no, go to step  5.
  3. Start the engine. Allow the engine to reach operating temperature. Change the throttle position more than 5 percent within 1 second, six times. Observe the HO2S voltage with a scan tool. Is the HO2S voltage outside 410-490 mV? If yes, go to next step. If no, go to step  5.
  4. Observe the Freeze Frame/Failure Records data for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC or as close to the Freeze Frame/Failure Records data that you observed. Does the DTC fail this ignition cycle? If yes, go to next step. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  5. Are both DTCs P0140 and P0160 set? If yes, go to next step. If no, go to step  7.
  6. Turn OFF the ignition. Disconnect the bank 1 sensor 2 HO2S connector. Probe the HO2S low reference circuit with a test lamp that is connected to battery voltage. Does the test lamp illuminate? If yes, go to step  11. If no, go to step  10.
  7. Turn OFF the ignition. Disconnect the affected HO2S connector. Jumper the HO2S high signal circuit to the low reference circuit. Turn ON the ignition, with the engine OFF. Observe the HO2S voltage with a scan tool. Is the HO2S voltage less than 200 mV? If yes, go to step  11. If no, go to next step.
  8. Turn OFF the ignition. Disconnect the PCM connector containing the HO2S high signal circuit. Test the HO2S high signal circuit for an open. Did you find and correct the condition? If yes, go to step  23. If no, go to next step.
  9. Test for an open between terminal "A" of the affected sensor harness connector and one of the following PCM terminals:
    • If DTC P0140 is set, use C1-28.
    • If DTC P0160 is set, use C1-25.

    Did you find and correct the condition? If yes, go to step  23. If no, go to step  18.

  10. Disconnect the PCM connector containing the HO2S low reference circuit. Test the low reference circuit for an open between HO2S bank 1 sensor 2 terminal "A" and PCM terminal C1-63. Did you find and correct the condition? If yes, go to step  23. If no, go to step  18.
  11. Remove the jumper from the previous step, if applicable. Is the O2B fuse open? If yes, go to step  14. If no, go to next step.
  12. Turn ON the ignition, with the engine OFF. Probe the affected HO2S ignition 1 voltage circuit with a test lamp that is connected to a good ground. Does the test lamp illuminate? If yes, go to next step. If no, go to step  19.
  13. Connect a test lamp between the affected HO2S ignition 1 voltage circuit and the HO2S heater ground circuit. Turn ON the ignition, with the engine OFF. Does the test lamp illuminate? If yes, go to step  17. If no, go to step  20.
  14. Disconnect the opposite bank HO2S pigtail connector. Test the HO2S ignition 1 voltage circuit for a short to ground. Replace the O2B fuse. Did you find and correct a short to ground in the ignition 1 voltage circuit? If yes, go to step  23. If no, go to next step.
    15. NOTE: Perform the following test on HO2S bank 1 sensor 2 and HO2S bank 2 sensor 2. A condition in either sensor will cause this DTC to set.
  15. Test the HO2S ignition 1 voltage circuit, sensor side, for a short to the HO2S body. Did you find the condition? If yes, go to step  21. If no, go to next step.
    16. NOTE: Perform the following test on HO2S bank 1 sensor 2 and HO2S bank 2 sensor 2. A condition in either sensor will cause this DTC to set.
  16. Measure the resistance between the HO2S ignition 1 voltage circuit, sensor side, and the HO2S heater ground circuit, sensor side. Does the resistance of either sensor measure above or below 2-50 ohms? If yes, go to step  21. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  17. Inspect for poor connections at the harness connector of the affected HO2S. Did you find and correct the condition? If yes, go to step  23. If no, go to step  21.
  18. Inspect for poor connections at the harness connector of the PCM. Did you find and correct the condition? If yes, go to step  23. If no, go to step  22.
  19. Repair the open in the ignition 1 voltage circuit. After repairs, go to step  23.
  20. Repair the open in the HO2S heater ground circuit. After repairs, go to step  23.
  21. Replace the affected HO2S. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  23.
  22. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  23. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  24. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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