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Home >> Pontiac >> 2001 >> Aztek Base, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics >> Diagnostic Tests >> DTC P0101: Mass Airflow Sensor System Performance >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
  2. Start engine. Using scan tool, monitor DTC information. If any other DTCs are set, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no other DTCs are set, go to next step.
  3. Observe and record FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Operate vehicle within conditions for running this DTC or as close to FREEZE FRAME/FAILURE RECORDS data observed. See CODE ENABLE CRITERIA . If DTC fails this ignition, go to next step. If DTC did not fail in this ignition, see DIAGNOSTIC AIDS .
  4. Operate engine at idle. Ensure engine is at normal operating temperature. Using scan tool, observe MAP sensor voltage parameter. If voltage parameter is 0.8-4.0 volts, go to next step. If voltage parameter is not 0.8-4.0 volts, diagnose MAP sensor. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article.
  5. Turn ignition off. Check for objects blocking MAF sensor air inlet screen. Check for plugged or collapsed intake air duct or dirty air filter element. Check for vacuum leaks in intake manifold, throttle body, EGR valve flange and pipe, MAF sensor seal, MAP sensor seal, EVAP canister purge valve seal, fuel meter body seal, PCV system, brake booster, and air induction system. Repair as necessary. After repairs, go to step  23. If no problem is found, go to next step.
  6. Turn ignition off. Remove vacuum source to MAP sensor. Leave harness connected. Connect a hand-held vacuum pump to MAP sensor. Turn ignition on, with engine off. Using scan tool, observe or record MAP sensor parameter display when vacuum is slowly applied at one in. Hg at a time up to 20 in. Hg. Each one in. Hg applied should result in a 3-4 kPa drop in MAP sensor value on scan tool. Value should change smoothly with each increase in vacuum. If MAP sensor value changes smoothly through the entire range of the test, go to next step. If MAP sensor value does not change smoothly through the entire range of the test, diagnose MAP sensor. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article.
  7. Apply 20 in. Hg to MAP sensor. If scan tool indicates that MAP sensor reading is 34 kPa or less, go to next step. If MAP sensor reading is not 34 kPa or less, diagnose MAP sensor. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article.
  8. Disconnect vacuum source from MAP sensor. If MAP sensor reading returns to original value observed in step  6, go to next step. If MAP sensor reading does not return to original value, diagnose MAP sensor. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article.
  9. Using scan tool, observe TP sensor angle parameter from closed throttle to wide open throttle (0-100 percent) position. If TP sensor value changes smoothly and completely, go to next step. If TP sensor value does not change smoothly, go to DTC P0121 .
  10. Turn ignition off. Disconnect MAF sensor harness connector. Turn ignition on, with engine off. Check voltage between ground and MAF sensor harness connector terminal "A" (Yellow wire). See Figure. If voltage reading is 5 volts, go to next step. If voltage reading is not 5 volts, go to step  12.
  11. Connect test light between MAF sensor harness connector terminals "B" (Black/White wire) and C" (Pink wire). If test light illuminates, go to step  19. If test light does not illuminate, go to step  14.
  12. If voltage reading is less than 4.5 volts, go to step  15. If voltage reading is not less than 4.5 volts, go to next step.
  13. Turn ignition off. Disconnect PCM harness connector. Turn ignition on, with engine off. Check voltage between ground and MAF sensor harness connector terminal "A" (Yellow wire). If voltage reading is about zero volts, go to step  22. If voltage reading is not about zero volts, go to step  18.
  14. Connect test light between ground and MAF sensor harness connector terminal "C" (Pink wire). If test light illuminates, go to step  16. If test light does not illuminate, go to step  17.
  15. Turn ignition off. Disconnect PCM harness connector. Check Yellow wire between PCM harness connector C1 terminal No. 69 and MAF sensor harness connector terminal "A" for high resistance, open circuit, or short to ground. See Figure and Figure . Repair as necessary. After repairs, go to step  23. If circuit is okay, go to step  20.
  16. Turn ignition off. Repair high resistance or open in Black/White wire. After repairs, go to step  23.
  17. Turn ignition off. Repair short to ground or open in Pink wire. Replace fuse if necessary. After repairs, go to step  23. If circuit is okay, go to step  21.
  18. Turn ignition off. Repair short to voltage in Yellow wire. After repairs, go to step  23.
  19. Turn ignition off. Check for poor connections at MAF sensor harness connector. Repair as necessary. After repairs, go to step  23. If connections are okay, go to step  21.
  20. Check for poor connections at PCM harness connector. Repair as necessary. After repairs, go to step  23. If connections are okay, go to step  22.
  21. Replace MAF sensor. After replacing sensor, go to step  23.
  22. Turn ignition off. Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  23. Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Operate vehicle within conditions for running this DTC. See CODE ENABLE CRITERIA . If DTC runs and passes, go to next step. If DTC resets, go to step  2.
  24. Using scan tool, observe stored information and CAPTURE INFO. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are displayed, system is okay.
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