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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 P0141 & P0161: Ho2S Heater Circuit - Bank 1 & 2, Sensors 2 (6.0L 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: The HO2S must be cool before proceeding with the diagnosis. The ignition must remain OFF for at least one-half hour before proceeding with diagnosis.

    If DTC P0300 is set, diagnose that DTC first. See DTC P0300: ENGINE MISFIRE DETECTED .

  2. Connect the scan tool. Setup the scan tool with the correct VIN information prior to turning the ignition ON. Turn ON the ignition, with the engine OFF. As quickly as possible, observe and record the HO2S voltage for the sensor that applies to this DTC. Monitor the HO2S voltage for 2 minutes. Does the voltage increase or decrease from the initial voltage by 150 mV? If yes, go to next step. If no, go to step  4.
  3. The condition that set this DTC is not present. This DTC may have been set by one of the following conditions:
    • An intermittently open or high resistance HO2S high signal circuit or low reference circuit.
    • An intermittently open or high resistance HO2S heater ignition 1 voltage or ground circuit.
    • A poor HO2S or PCM connector terminal contact.
    • A defective HO2S.

    Repair any of the above conditions as necessary. Did you find and correct the condition? If yes, go to step  14. If no, see DIAGNOSTIC AIDS .

  4. Turn OFF the ignition. Disconnect the HO2S connector for the sensor that applies to this DTC. Connect a test lamp between the HO2S heater ignition 1 voltage and ground circuit terminals. Turn ON the ignition, with the engine OFF. Does the test lamp illuminate? If yes, go to next step. If no, go to step  6.
  5. Disconnect the test lamp. Jumper the HO2S low reference circuit terminal to a known-good ground. Jumper the HO2S high signal circuit terminal to a known-good ground. Use the scan tool in order to monitor the HO2S voltage for the sensor that applies to this DTC. Turn the ignition ON, with the engine OFF. Is the voltage less than 20 mV? If yes, go to step  8. If no, go to step  7.
  6. Connect the test lamp between the HO2S heater ignition 1 voltage circuit terminal and a known-good ground. Turn the ignition ON, with the engine OFF. Does the test lamp illuminate? If yes, go to step  9. If no, go to step  10.
  7. Turn OFF the ignition. Remove the jumpers from the PCM connector containing the HO2S high and low reference circuits. Use a Digital Multimeter (DMM) in order to measure the continuity of the HO2S high signal circuit and the HO2S low reference circuit between the PCM connector terminal and the HO2S connector terminal. Is the resistance less than 5 ohms? If yes, go to step  12. If no, go to step  11.
  8. Replace the affected HO2S. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  14.
  9. Repair the open HO2S heater ground circuit. After repairs, go to step  14.
  10. Repair the lack of voltage on the HO2S heater ignition 1 voltage circuit. If the fuse is open, repair the short to ground on the circuit. An open fuse or a lack of voltage to the fuse may cause other DTCs or symptoms to be present. After repairs, go to step  14.
  11. Repair the circuit that has a high resistance. After repairs, go to step  14.
  12. Inspect for proper PCM terminal contact. Repair the PCM terminals as necessary. Did you complete the repair? If yes, go to step  14. If no, go to next step.
  13. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  14. 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.
  15. 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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