Diagnosis & Repair
WARNING: This page is about a different car, the 2003 Lexus RX 300. 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. Turn on scan tool. Start engine and allow it to idle. Monitor MAF rate. If scan tool reading is 0.0 gm/sec., go to next step. If reading is 271.0 gm/sec. or more once engine is at normal operating temperature, go to step 5.
- Disconnect MAF sensor connector. Turn ignition on. Using voltmeter, measure voltage between ground and terminal No. 1 (Black/Red wire) at MAF sensor wiring harness connector. See Fig 1. If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check for open in Black/Red wire between MAF sensor connector and EFI relay. EFI relay is located in junction block at left side of engine compartment. If circuit is okay, check EFI relay. See RELAYS under RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING - ES300 & RX300 article.
- Access ECM behind glove box. Start engine. Ensure that transmission is in PARK or NEUTRAL position, and A/C is turned off. Backprobing ECM connector, measure voltage between ground and terminal VG. See Fig 2 and Fig 4 . If voltage is 1.1-1.5 volts, replace ECM and retest system.
- If voltage is not 1.1-1.5 volts, locate and repair open or short circuit in Yellow/Red wire between MAF sensor and ECM E8 connector. If Yellow/Red wire is okay, replace MAF sensor and retest system.
- Access ECM behind glove box. Turn ignition off. Backprobing ECM E8 connector, check for continuity between ground and terminal E2G. See Fig 3 and Fig 4 . If continuity does not exist, replace ECM and retest system. If continuity exists, go to next step.
- Check for an open in Green/Black wire between MAF sensor and ECM E8 connector. Repair as necessary. If circuit is okay, replace MAF sensor.