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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 108 (Engine Controls Self-Diagnostics - 2.2L) >> Diagnostic Tests >> DTC P0140: Ho2S 2 Circuit - Insufficient Activity (DOHC) >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Pontiac Sunfire, 2002 Pontiac Grand Am, 2002 Oldsmobile Alero, and 2002 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
  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. Operate the engine at normal operating temperature. Operate the engine at greater than 1200 RPM for 2 minutes. With a scan tool, observe the HO2S 2 voltage parameter. Does the scan tool indicate HO2S 2 voltage varying at greater than and less than the specified values of 350-550 millivolts? If yes, go to next step. If no, go to step  4.
  3. Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See CONDITIONS FOR RUNNING DTC . Does the scan tool indicate that this DTC failed this ignition? If yes, go to next step. If no, refer to INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  4. Turn ignition off. Disconnect HO2S 2. Turn ignition on, with engine off. Using a Digital Multimeter (DMM), measure the voltage of the HO2S 2 high signal circuit on the PCM side to a good ground. Does the voltage measure within 350-550 millivolts? If yes, go to next step. If no, go to step  7.
  5. Turn ignition off. Connect a 3-amp fused jumper wire between the HO2S 2 harness connector high signal circuit and low signal circuit. Turn ignition on. Use a scan tool in order to monitor the HO2S 2 voltage for the sensor that applies to this DTC. Does the scan tool indicate that the HO2S 2 voltage is less than 20 millivolts? If yes, go to step  8. If no, go to next step.
  6. Test the HO2S 2 low signal circuit for an open, high resistance or short to voltage. Did you find and correct the condition? If yes, go to step  13. If no, go to step  10.
  7. Test the HO2S 2 high signal circuit for open, high resistance or short to voltage. Did you find and correct the condition? If yes, go to step  13. If no, go to step  10.
    8. NOTE: Before replacing the suspected HO2S, check and remove any source of contamination.
  8. Inspect for use of incorrect silicone RTV sealant, fuel contamination, exhaust leak, incorrectly installed HO2S or damaged wiring. Did you find and correct the condition? If yes, go to step  13. If no, go to next step.
  9. Test for poor connections at the harness connector of the HO2S 2. Did you find and correct the condition? If yes, go to step  13. If no, go to step  11.
  10. Test for poor connections at the harness connector of the PCM. Did you find and correct the condition? If yes, go to step  13. If no, go to step  12.
    11. NOTE: Determine the cause of contamination before replacing the sensor.
    Replace HO2S 2. When complete, go to step  13.
  12. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE REPROGRAMMING  under PROGRAMMING. After replacing PCM, go to next step.
  13. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  14. With a scan tool, observe the stored information, Capture Info. 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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