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Home >> Lexus >> 1995 >> LS 400 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - OBD-II >> Diagnostic Testing >> Code P0100: Mass Airflow (MAF) Sensor Circuit >> Diagnosis & Repair Procedure

Diagnosis & Repair Procedure

  1. Connect scan tester to Data Link Connector (DLC) No. 3. See Figure. Start engine and allow it to idle. Turn on scan tester. Monitor MAF flow rate. If scan tester reading is 0.0 gm/sec., go to next step. If reading is 9.0-21.0 gm/sec. once engine is at normal operating temperature, go to step 5).
  2. Disconnect MAF sensor harness connector. Ensure ignition is on. Using DVOM, measure voltage between ground and terminal No. 1 (Black/Red wire) at MAF sensor connector. If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, locate and repair open in Black/Red wire between MAF sensor connector and ECM.
  3. Access ECM behind glove box. Start engine. Backprobing ECM connector, check voltage between ground and terminal No. 8 (Blue/Yellow wire) at ECM E13 connector. See Figure. If voltage is 1.1- 1.5 volts, replace ECM and retest.
  4. If voltage is not 1.1-1.5 volts, locate and repair open or short circuit in Blue/Yellow wire between MAF sensor and ECM. If Blue/Yellow wire is okay, replace MAF sensor and retest.
  5. Access ECM behind glove box. Turn ignition off. Backprobing ECM connector, check for continuity between ground and terminal No. 21 (Green/White wire) at ECM E13 connector. If continuity does not exist, replace ECM and retest. If continuity exists, locate and repair open in Green/White wire between MAF sensor and ECM. If Green/White wire is okay, replace MAF sensor.
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