Diagnosis & Repair

WARNING: This page is about a different car, the 2003 Lexus SC 430. However, it is still accessible from the selected car via links, so may be relevant.

Connect scan tool to Data Link Connector (DLC) No. 3. See Figure. Turn ignition on. Start engine and allow it to idle. Using scan tool, monitor MAF rate. If scan tool reading is 0.0 gram/second, go to next step. If reading is 271.0 grams/second or more, go to step 3.
Disconnect MAF sensor connector. See Fig 1. Turn ignition on. Using DVOM, measure voltage between terminal No. 1 and ground. If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, locate and repair open wiring between MAF sensor connector and ECM.

Fig 1: Identifying MAF Sensor Connector Terminals
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Access ECM at left front of engine compartment. Start engine. Ensure transmission is in Park or Neutral and A/C is off. Backprobing connector, measure voltage between terminals E1 and VG at ECM E4 connector. See Fig 5-Fig 6 . If voltage is .5-3.0 volts, go to next step. If voltage is not .5-3.0 volts, check and replace ECM.
Check for an open or short in wiring between ECM and MAF sensor. See Fig 2-Fig 3 . See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair wiring harness as necessary. Also check ECM ground between terminals E1 and EVG of ECM connectors E3 and E4. See Fig 4. If wiring is okay, replace airflow meter assembly.

Fig 2: Identifying MAF Sensor Connector Terminals EVG & VG
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Fig 3: Locating ECM Connector Terminals EVG, VG & E1
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Fig 4: Identifying ECM Connector Terminals E1 & EVG
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Fig 5: Identifying ECM Connector Terminals E1 & VG
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Fig 6: Identifying Engine Control Module (ECM) Connectors & Terminals
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