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Home >> GMC >> 1997 >> Forward Control 4.3 W, L35, Automatic >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 11 (Engine Controls - Tests W/Codes - 7.4L (P Series)) >> Diagnostic Trouble Codes >> DTC P1133 - Ho2S Insufficient Switching Bank 1, Sensor 1 >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different variant/trim than selected.
  1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the F - BASIC TESTING - 7.4L article. After performing OBD system check, go to next step.
  2. Check if any other DTCs are set. If any other DTCs are set, go to applicable DTC test. If no other DTCs are set, go to step 3).
  3. Install scan tool. With engine idling, monitor MAP sensor voltage using scan tool. If MAP sensor voltage is greater than 4 volts, go to DTC P0108 . If MAP sensor voltage is not greater than 4 volts, go to next step.
  4. Check for the following conditions:
    • Air intake duct for improper installation.
    • Air intake duct for collapsed or restriction, for missing or plugged air filter.
    • Throttle body and intake manifold for vacuum leaks.
    • Throttle body for damage to inlet or for foreign objects partially blocking inlet.
    • Throttle body for coking or objects blocking IAC valve passages.
    • Exhaust system for corrosion, leaks, loose or missing hardware.
    • HO2S is installed securely and pigtail harness is not contacting exhaust manifold or wires.
    • Vacuum hoses for splits, kinks and proper connections.
    • Fuel for excessive water, alcohol or other contaminants.
    • VCM sensor grounds are clean, tight and in proper locations.
    • Fuel pressure regulator.

    If a problem was found, go to next step. If a problem was not found, go to step 6).

  5. Repair or replace as necessary. After repairs, go to step 10).
  6. Perform injector coil test. See the SYSTEM/COMPONENT TESTS article. If a problem was found, go to step 9). If a problem was not found, go to next step.
  7. Remove HO2S bank, 1 sensor 1 and inspect for contamination. If contamination is present, go to next step. If contamination is not present, see DIAGNOSTIC AIDS.
  8. Replace HO2S bank 1, sensor 1. After replacing HO2S sensor, go to step 10).
  9. Replace fuel injector. After replacing injector, go to step 10).
  10. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P1133. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2).
  11. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.
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