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Home › Mitsubishi › 1997 › Montero LS › Repair and Diagnosis › Engine Performance › System › Engine Controls - Tests W/Codes › Circuit Tests › DTC P0100: Volume Airflow (VAF) Sensor Circuit Failure › Test Procedures

Test Procedures

NOTE: Do not replace the Engine Control Module (ECM) until a through terminal check reveals there are no short/open circuits. Check that the ECM ground circuit is normal before checking for the cause of the problem.
NOTE: Procedures are provided by manufacturer for component testing using an engine analyzer with oscilloscope capability. Refer to manufacturer's operation manual for instructions in use of oscilloscope.
  1. If using scan tool, go to step 3). Disconnect VAF sensor connector. Install Test Harness (MB991348) between VAF sensor and connector. Using engine analyzer with oscilloscope capability, connect special patterns probe to VAF sensor connector terminal No. 3 or to ECM connector terminal No. 90.
  2. Start engine. Verify waveform high frequency and low frequency patterns are of about the same length (time). Verify wavelength decreases and frequency increases as engine RPM increases. If conditions are not as specified, replace VAF sensor. If conditions are as specified, go to step 4).
  3. Warm vehicle to normal operating temperature. Ensure headlights and accessories are off. Using scan tool, read VAF sensor value (frequency). See VOLUME AIRFLOW SENSOR VALUES  table. Frequency should increase when engine is raced. If values are not as specified, replace VAF sensor. If values are as specified, disconnect VAF sensor connector and go to next step.
    VOLUME AIRFLOW SENSOR VALUES

    Application Hz @ 700 RPM Hz @ 2000 RPM
    Montero 25-51 80-120
  4. Disconnect MFI relay connector. Using DVOM, check for continuity between VAF sensor connector terminal No. 4 and MFI relay connector terminal No. 1. If continuity does not exist, repair wiring harness as necessary. If continuity exists, go to next step.
  5. Turn ignition switch to OFF position. Disconnect ECM connector. Ground ECM connector terminal No. 19. Using DVOM, check for continuity between chassis ground and VAF sensor connector terminal No. 7. If continuity does not exist, repair wiring harness as necessary. If continuity exists, go to next step.
  6. Ground ECM connector terminal No. 90. Using DVOM, check for continuity between chassis ground and VAF sensor connector terminal No. 3. If continuity does not exist, repair wiring harness as necessary. If continuity exists, turn ignition switch to ON position and go to step 9).
  7. Using DVOM, check voltage between chassis ground and VAF sensor connector terminal No. 3. If voltage is not 4.8-5.2 volts, replace ECM. If voltage is as specified, condition required to set DTC is not present at this time. Go to next step.
  8. Test is complete. Intermittent problem may exist. Road test vehicle (if necessary) and attempt to duplicate conditions that caused original complaint. Recheck for DTCs. If no DTCs are displayed, go to INTERMITTENT DTCS  .
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