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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 239 (ENGINE CONTROLS SELF-DIAGNOSTICS - 3.1L ENGINE)DIAGNOSTIC TESTSP0130: HO2S 1 CIRCUIT CLOSED LOOP PERFORMANCEDIAGNOSTIC PROCEDURE
1999 GMC Forward Control 5.7 R, Automatic

Diagnostic Procedure

1999 GMC Forward Control 5.7 R, AutomaticSECTION Diagnostic Procedure
WARNING: This page is about a different car, the 2003 Pontiac Grand Prix, 2003 Chevrolet Malibu, and 2003 Buick Century. 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. Start the engine. Allow the engine to idle at operating temperature. Observe the Heated Oxygen Sensor (HO2S) 1 voltage parameter using a scan tool. Wait 15 seconds to allow the HO2S 1 heater current to stabilize. Does the HO2S 1 voltage fluctuate rapidly above and below 350-550 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 switch to OFF position for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running Test. See CONDITIONS FOR RUNNING TEST . 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, go to INTERMITTENTS in TROUBLE SHOOTING - 3.1L CENTURY, GRAND PRIX & MALIBU article.
  4. Turn ignition switch to OFF position. Disconnect the HO2S 1 harness connector. Turn ignition switch to RUN position, engine OFF. Measure the voltage from the HO2S 1 harness connector high signal circuit, on the engine harness side, to a good ground using a DMM. Is the HO2S 1 voltage 0.425-0.500 volt? If yes, go to next step. If no, go to step  6.
  5. Turn ignition switch to OFF position. Connect a 3-amp fused jumper wire between the HO2S 1 high signal circuit of the engine harness and the HO2S 1 low reference circuit of the engine harness. Turn ignition switch to RUN position, engine OFF. Observe the HO2S 1 voltage using a scan tool. Is the HO2S 1 voltage less than 25 mV? If yes, go to step  8. If no, go to next step.
  6. Turn ignition switch to OFF position. Disconnect both PCM connectors. Measure the resistance of each of the following circuits using a DMM:
    • HO2S 1 high signal circuit between HO2S connector and the PCM connector.
    • HO2S 1 low reference circuit between HO2S connector and the PCM connector.
    • HO2S 1 low reference loop between PCM harness connector C1 terminal No. 29 and PCM harness connector C2 terminal No. 80.

    Is the resistance of each circuit less than 5 ohms? If yes, go to step  11. If no, go to next step.

  7. Repair the circuit that measured a high resistance or an open. After repair, go to step  14.
  8. Remove the jumpers from the HO2S 1 terminals. Connect a test light between the HO2S 1 ignition voltage circuit and the HO2S 1 heater low control circuit terminals, on the engine harness side. Start the engine. Does the test light illuminate? If yes, go to next step. If no, go to step DTC P0135: HO2S 1 HEATER PERFORMANCE .
  9. Check for the following that may affect the HO2S operation:
    • HO2S for contamination.
    • Chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring.
    • The HO2S must have a clean air reference to function properly. This clean air reference is obtained by way of the HO2S wires. Obstruction of the air reference and degraded HO2S performance could result from any attempt to repair the above conditions.
    • Exhaust system leaks or restrictions. See EXHAUST SYSTEM CHECK in SYSTEM & COMPONENT TESTING - 3.1L CENTURY, GRAND PRIX & MALIBU article.
    • Evaporative Emissions (EVAP) system malfunction. EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 3.1L CENTURY, GRAND PRIX & MALIBU article.
    • The fuel pressure. Incorrect fuel pressure can affect HO2S operation. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 3.1L CENTURY, GRAND PRIX & MALIBU article.

    Did you find and correct the condition? If yes, go to step  14. If no, go to next step.

  10. Test for an intermittent and for a poor connection at the HO2S 1 harness connector. Did you find and correct the condition? If yes, go to step  14. If no, go to step  12.
  11. Test for an intermittent and for a poor connection at the PCM harness connector. Did you find and correct the condition? If yes, go to step  14. If no, go to step  13.
  12. Replace the HO2S 1 sensor. After repair, go to step  14.
  13. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL & INSTALLATION article. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  14. Using scan tool, clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running Test. See CONDITIONS FOR RUNNING TEST . 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 step  2. If no, go to next step.
  15. Using the scan tool, observe the stored information in CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay at this time.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.