Diagnostic Procedure
WARNING: This page is about a different car, the 2004 Lexus ES 330. However, it is still accessible from the selected car via links, so may be relevant.
- Turn ignition switch to ON position. Using Lexus hand-held tester, clear DTCs in occupant classification ECU. See CLEARING PASSENGER OCCUPANT CLASSIFICATION SYSTEM DTCS USING LEXUS HAND-HELD TESTER under DIAGNOSTICS. Clear DTCs in air bag sensor assembly. See CLEARING DIAGNOSTIC TROUBLE CODES (DTCS) under DIAGNOSTICS. Turn ignition switch to LOCK position. Turn ignition switch to ON position. Retrieve DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES (DTCS) under DIAGNOSTICS. If no DTC is retrieved, go to next step. If DTCs B1795 and B1771 are retrieved, perform diagnostic test B1771 first. If DTC B1795 is retrieved, go to step 3.
- Remove ECU-B fuse (10 amp). See Fig 1. Measure resistance across fuse blades. If resistance is less than one ohm, reinstall fuse and go to next step. If resistance is more than one ohm, replace fuse.
- Turn ignition switch to LOCK position. Disable air bag system. See DISABLING SYSTEM under DISABLING & ACTIVATING AIR BAG SYSTEM. Access occupant classification ECU and disconnect harness connector O4. See OCCUPANT CLASSIFICATION ELECTRONIC CONTROL UNIT (ECU) under REMOVAL & INSTALLATION. Connect negative battery cable. Turn ignition switch to ON position. Measure voltage between ground and harness side of occupant classification ECU connector O4, terminal No. 1 (Red wire, circuit B+). See Figure. Measure resistance between ground and harness side of occupant classification ECU connector O4, terminal No. 3 (Brown wire, circuit GND). If voltage in Red wire is 10-14 volts, and resistance in Brown wire is less than one ohm, check for intermittent fault. See AIR BAG WARNING LIGHT INTERMITTENT . If voltage in Red wire is not 10-14 volts, or resistance in Black/White wire is more than one ohm, repair or replace wiring harness or battery.
- Replace occupant classification ECU. Perform occupant classification ECU initialization. See OCCUPANT CLASSIFICATION ELECTRONIC CONTROL UNIT (ECU) INITIALIZATION PROCEDURE .