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Home >> GMC >> 1996 >> Forward Control 4.3 Z, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - P Series (Gasoline) >> Diagnostic Trouble Codes >> DTC P0101 - MAF Sensor System Performance >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
  2. Install scan tool. Turn ignition on, with engine off. Using scan tool, review and record FAILURE RECORDS data. Operate vehicle within FAILURE RECORDS conditions. Using scan tool, monitor SPECIFIC DTC for DTC P0101. If scan tool indicates DTC P0101 FAILED THIS IGN, go to next step. If scan tool does not indicate DTC P0101 FAILED THIS IGN, see DIAGNOSTIC AIDS.
  3. Check for the following conditions and repair as necessary:
    • Objects blocking throttle body inlet screen.
    • Intake manifold vacuum leaks.
    • Vacuum leaks at throttle body.
    • Vacuum leaks at EGR valve flange and pipes.
    • Crankcase ventilation valve faulty, missing or incorrectly installed.

    If a problem was found, go to step 17). If a problem was not found, go to next step.

  4. Turn ignition on, with throttle closed. Using scan tool, observe TP ANGLE display. If TP angle is near zero, go to next step. If TP angle is not near zero, go to DTC P0121.
  5. Turn ignition off. Disconnect MAF sensor connector. Turn ignition on, with engine off. Using DVOM, check voltage between ground and MAF sensor connector signal circuit. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 7).
  6. Connect test light between MAF ignition feed circuit and ground circuit of MAF sensor connector. If test light illuminates, go to step 10). If test light does not illuminate, go to step 9).
  7. If voltage is less than 4.5 volts, go to step 11). If voltage is not less than 4.5 volts, go to next step.
  8. Turn ignition off. Disconnect VCM connector. Turn ignition on, with engine off. Check voltage between MAF signal circuit of VCM connector and ground. If voltage is zero volts, go to step 16). If voltage is not zero volts, go to step 14).
  9. Connect test light between MAF ignition feed circuit of MAF sensor connector and ground. If test light illuminates, go to step 12). If test light does not illuminate, go to step 13).
  10. Check for poor connection at MAF sensor and repair as necessary. If poor connection is present, go to step 17). If poor connection is not present, go to step 15).
  11. Check for open, short to ground or short to MAF sensor ground circuit in MAF signal circuit between MAF sensor and VCM. Repair as necessary. If MAF signal circuit is open or shorted, go to step 17). If MAF signal circuit is not open or shorted, go to step 16).
  12. Locate and repair open in ground circuit between MAF sensor and VCM. Go to step 17).
  13. Locate and repair open in MAF ignition feed circuit to MAF sensor. Go to step 17).
  14. Locate and repair short to voltage in MAF signal circuit between sensor and VCM. Go to step 17).
  15. Replace MAF sensor. Go to step 17).
  16. Replace VCM. Go to next step.
  17. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select SPECIFIC DTC, then enter DTC P0101. 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).
  18. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.
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