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 LOCK position. Disable air bag system. See DISABLING SYSTEM under DISABLING & ACTIVATING AIR BAG SYSTEM. Reconnect air bag sensor assembly harness connectors. Connect negative battery cable and wait at least 2 seconds. Turn ignition switch to ON position and observe AIR BAG warning light. AIR BAG warning light should come on. Turn ignition switch to LOCK position. Disconnect negative battery cable and wait at least 90 seconds. Disconnect air bag sensor assembly harness connectors. Connect negative battery cable and wait at least 2 seconds. Turn ignition switch to ON position and observe AIR BAG warning light. AIR BAG warning light should go out 10 seconds after ignition switch is turned to ON position, and then illuminate again. If AIR BAG warning light operates as described, go to next step. If AIR BAG warning light does not operate as described, replace instrument cluster. See INSTRUMENT CLUSTER under REMOVAL & INSTALLATION.
- Access instrument cluster and disconnect harness connectors. Measure resistance between harness side of air bag sensor assembly connector A31, terminal No. 14 (Black/Yellow wire, circuit LA) and harness side of instrument cluster connector C7, terminal No. 12 (White wire, circuit LA). See Fig 1 & Fig 2 . Resistance should be less than one ohm. Measure resistance between ground and harness side of air bag sensor assembly connector A31, terminal No. 14. Resistance should be more than one megohm. Ensure ignition switch is in ON position. Measure voltage between ground and harness side of air bag sensor assembly connector A31, terminal No. 14. Voltage should be less than one volt. If voltage and resistance readings are normal, go to next step. If voltage and resistance readings are not normal, replace wire harness between instrument cluster and air bag sensor assembly.
- Connect instrument cluster harness connectors. Ensure negative battery cable is connected and ignition switch is in ON position. Measure voltage between ground and harness side of instrument cluster connector C7, terminal No. 40 (White wire). If voltage is 8-14 volts, go to next step. If voltage is not 8-14 volts, replace instrument cluster.
- Turn ignition switch to LOCK position. Disconnect negative battery cable. Wait at least 90 seconds. Replace air bag sensor assembly. See AIR BAG SENSOR ASSEMBLY under REMOVAL & INSTALLATION. Connect negative battery cable and wait at least 2 seconds. Perform system operation check. See SYSTEM OPERATION CHECK . If AIR BAG warning light operates normally, test is complete. If AIR BAG warning light does not operate normally, replace instrument cluster.