LEMON Manuals: Even more car manuals for everyone
Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Controls - Self-Diagnostics - 4.3L >> Diagnostic Tests >> DTC P0140: Ho2S Circuit - Insufficient Activity (Bank 1, Sensor 2) >> Diagnostic Procedures

Diagnostic Procedures

  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. Start engine. Allow the engine to reach operating temperature. Refer to Scan Tool Data List. Operate engine at 1500 RPM for 30 seconds. While observing the affected HO2S voltage parameter with a scan tool, quickly cycle the throttle from closed throttle to wide-open throttle 3 times. Did the HO2S voltage parameter change more than 200 mV? If yes, go to next step. If no, go to step  4.
  3. Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to next step. If no, problem is intermittent. Go to Intermittent Conditions INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article.
  4. Turn ignition off. Disconnect the affected HO2S. Turn ignition on, with engine off. Observe the HO2S voltage parameter with a scan tool. Is the HO2S voltage parameter more than 800 mV? If yes, go to step  6. If no, go to next step.
  5. Measure the voltage from the high signal circuit of the HO2S harness connector on the engine harness side to a good ground with a DVOM. Is the voltage more than 0.2 volt? If yes, go to step  7. If no, go to step  8.
    6. NOTE: The sensor may be damaged if the circuit is shorted to a voltage source.
  6. Test the HO2S high signal circuit for a short to voltage. Did you find and correct the condition? If yes, go to step  16. If no, go to step  13.
  7. Measure the voltage from the low signal circuit of the HO2S harness connector on the engine harness side to a good ground with a DVOM. Is the voltage more than 2 volts? If yes, go to step  11. If no, go to step  9.
  8. Test the HO2S high signal circuit for an open. Did you find and correct the condition? If yes, go to step  16. If no, go to step  13.
  9. Connect a 3-amp fused jumper wire between the high signal circuit of the HO2S harness connector on the engine harness side and the low signal circuit of the HO2S harness connector on the engine harness side. Observe the HO2S voltage parameter with a scan tool. Is the HO2S voltage parameter less than 100 mV? If yes, go to step  12. If no, go to next step.
  10. Test the HO2S low signal circuit for an open. Did you find and correct the condition? If yes, go to step  16. If no, go to step  13.
  11. Test the HO2S low signal circuit for a short to voltage. Did you find and correct the condition? If yes, go to step  16. If no, go to step  13.
  12. Test for an intermittent and for a poor connection at the HO2S. Did you find and correct the condition? If yes, go to step  16. If no, go to step  14.
  13. Test for an intermittent and for a poor connection at the PCM. Did you find and correct the condition? If yes, go to step  16. If no, go to step  15.
  14. Replace affected HO2S. See appropriate REMOVAL & INSTALLATION article. After repairs, go to step  16.
  15. Replace PCM. See appropriate REMOVAL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  16. Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running DTC. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  17. 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.
scientia non olet · About LEMON Manuals