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Home >> Toyota >> 2001 >> Sienna CE >> Repair and Diagnosis >> External Pages >> Different car >> Section 269 (Air Bag Restraint Systems) >> Diagnostic Tests >> DTC B1793: Occupant Classification Sensor Power Supply Circuit Malfunction >> Diagnostic Procedure

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.
  1. Turn ignition switch to ON position. Clear DTCs in air bag sensor assembly. See CLEARING DIAGNOSTIC TROUBLE CODES (DTCS)  under DIAGNOSTICS. 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. Turn ignition switch to LOCK position. Turn ignition switch to ON position. Retrieve DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES (DTCS)  under DIAGNOSTICS. If DTC B1793 is retrieved, go to next step. If DTC B1793 is not retrieved, check for intermittent fault. See AIR BAG WARNING LIGHT INTERMITTENT .
  2. Turn ignition switch to LOCK position. Disable air bag system. See DISABLING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM. Access occupant classification ECU. See OCCUPANT CLASSIFICATION ELECTRONIC CONTROL UNIT (ECU)  under REMOVAL & INSTALLATION. Check for proper connection of occupant classification sensor connectors and occupant classification ECU connectors. If connectors are properly connected, go to next step. If connectors are not properly connected, connect connectors and go to step  1.
  3. Disconnect occupant classification ECU connector O3. Disconnect all occupant classification sensor connectors. Connect negative battery cable. Turn ignition switch to ON position. Measure voltage between ground and harness side of occupant classification ECU connector 03, terminal No. 5 (Gray wire, circuit SVC3). See Figure. Measure voltage between ground and harness side of occupant classification ECU connector 03, terminal No. 6 (Violet wire, circuit SVC4). Measure voltage between ground and harness side of occupant classification ECU connector 03, terminal No. 11 (Red wire, circuit SVC1). Measure voltage between ground and harness side of occupant classification ECU connector 03, terminal No. 12 (White wire, circuit SVC2). If voltage is more than one volt, repair or replace wiring harness between occupant classification ECU and appropriate occupant classification sensor. If voltage is less than one volt, go to next step.
  4. Turn ignition switch to LOCK position. Disconnect negative battery cable. Wait at least 90 seconds. Measure resistance between ground and harness side of occupant classification ECU connector 03, terminal No. 5. Measure resistance between ground and harness side of occupant classification ECU connector 03, terminal No. 6. Measure resistance between ground and harness side of occupant classification ECU connector 03, terminal No. 11. Measure resistance between ground and harness side of occupant classification ECU connector 03, terminal No. 12. If resistance is less than one megohm, repair or replace wiring harness between occupant classification ECU and appropriate occupant classification sensor. If resistance is more than one megohm, go to next step.
  5. Measure resistance between harness side of occupant classification ECU connector 03, terminal No. 5 and harness side of occupant classification left rear sensor connector O6, terminal No. 1. See Figure & Figure . Measure resistance between harness side of occupant classification ECU connector 03, terminal No. 6 and harness side of occupant classification right rear sensor connector O8, terminal No. 1. Measure resistance between harness side of occupant classification ECU connector 03, terminal No. 11 and harness side of occupant classification left front sensor connector 05, terminal No. 1. Measure resistance between harness side of occupant classification ECU connector 03, terminal No. 12 and harness side of occupant classification right front sensor connector 07, terminal No. 1. If resistance is more than one ohm, repair or replace wiring harness between occupant classification ECU and appropriate occupant classification sensor. If resistance is less than one megohm, go to next step.
  6. Measure resistance between harness side of occupant classification ECU connector 03, terminals No. 5 and 6. Measure resistance between harness side of occupant classification ECU connector 03, terminals No. 6 and 11. Measure resistance between harness side of occupant classification ECU connector 03, terminals No. 11 and 12. Measure resistance between harness side of occupant classification ECU connector 03, terminals No. 5 and 12. Measure resistance between harness side of occupant classification ECU connector 03, terminals No. 6 (Violet wire) and No. 6 and 12. Measure resistance between harness side of occupant classification ECU connector 03, terminals No. 5 and 11. If resistance is less than one megohm, repair or replace wiring harness between occupant classification ECU and appropriate occupant classification sensor. If resistance is more than one megohm, go to next step.
  7. Connect occupant classification ECU connector 03 and all occupant classification sensor connectors. Connect negative battery cable. Turn ignition switch to ON position. Using Lexus hand-held tester, clear DTCs in occupant classification ECU. Clear DTCs in air bag sensor assembly. Turn ignition switch to LOCK position. Turn ignition switch to ON position. Retrieve DTCs. If DTC B1793 is retrieved, go to next step. If DTC B1793 is not retrieved, check for intermittent fault.
  8. Turn ignition switch to LOCK position. Disconnect negative battery cable. Wait at least 90 seconds. Replace occupant classification ECU. Perform occupant classification ECU zero point calibration. See step  1, Zero point calibration, under . If COMPLETE is displayed at end of zero point calibration, go to next step. If COMPLETE is not displayed at end of zero point calibration, go to step  11.
  9. Perform occupant classification ECU sensitivity check. See step 2 , Sensitivity check under . If sensitivity check is within standard, go to next step. If sensitivity check is not within standard, go to step  11.
  10. Connect negative battery cable. Turn ignition switch to ON position. Using Lexus hand-held tester, clear DTCs in occupant classification ECU. Clear DTCs in air bag sensor assembly. Turn ignition switch to LOCK position. Turn ignition switch to ON position. Retrieve DTCs. If DTC B1793 is retrieved, go to next step. If DTC B1793 is not retrieved, check for intermittent fault.
  11. Turn ignition switch to LOCK position. Wait at least 90 seconds. Replace left front seat adjuster. See FRONT SEAT ADJUSTER FRAME  under REMOVAL & INSTALLATION. Perform occupant classification ECU initialization.
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