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Home >> Chevrolet >> 1997 >> C3500 HD 7.4 J, Automatic >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 3 (Engine Controls - Tests W/Codes - 6.5L) >> Diagnostic Trouble Codes >> DTC P0101 - Mass Airflow System Performance >> 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 BASIC TESTING - 6.5L DIESEL article. Then go to next step.
  2. Turn ignition on, with engine off. Review and record scan tool Fail Records data. Operate vehicle within the Fail Records conditions. Using scan tool, monitor Specific DTC info for DTC P0101. If scan tool indicates that DTC P0101 failed this ignition cycle, go to next step. If scan tool does not indicate that DTC P0101 failed, see DIAGNOSTIC AIDS.
  3. Check for plugged intake air duct, dirty air filter, intake manifold vacuum leaks or EGR leak. Repair or replace as necessary. After repairs, go to step 17). If no problems were found, go to next step.
  4. Turn ignition on, with engine off. Ensure throttle is closed. Observe APP angle display on scan tool. APP angle should be zero percent. If APP angle is as specified or close to zero percent, go to next step. If APP angle is not as specified, see DTC P0121 for diagnosis.
  5. Turn ignition off. Disconnect MAF sensor harness connector. Turn ignition on, with engine off. Using a DVOM, check voltage between MAF sensor harness connector terminal "A" (signal circuit) and chassis ground. DVOM should read 5 volts. If voltage reading is as specified, go to next step. If voltage reading is not as specified, go to step 7).
  6. Connect a test light between MAF sensor harness connector terminals "C" (ignition feed circuit) and "B" (ground circuit). If test light illuminates, go to step 10). If test does not illuminate, go to step 9).
  7. If voltage reading is less than 4.5 volts, go to step 11). If voltage reading is greater than 4.5 volts, go to next step.
  8. Turn ignition off. Disconnect PCM harness connector. Turn ignition on, with engine off. Check voltage between MAF sensor harness connector terminal "A" and ground. If voltage reading is zero volts, go to step 15). If voltage reading is not zero volts, go to step 13).
  9. Connect test light between MAF sensor harness connector terminal "C" and chassis 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. Repair or replace terminals as necessary. After repairs, go to step 17). If terminals are okay, go to step 15).
  11. Check MAF signal circuit between PCM and MAF sensor for an open, short to ground, or short to MAF sensor ground circuit. Repair as necessary. After repairs, go to step 17). If circuits are okay, go to step 16).
  12. Locate and repair open in ground circuit to MAF sensor. After repairs, go to step 17).
  13. Locate and repair open in ignition feed circuit to MAF circuit. After repairs, go to step 17).
  14. Locate and repair short to voltage in MAF sensor signal circuit. After repairs, go to step 17).
  15. Replace MAF sensor. After replacing sensor, go to step 17).
  16. Replace PCM. After replacing PCM, go to next step.
  17. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC number that was set. 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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