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Test No. 29: Body Electronic Control Unit Does Not Operate

  1. Note location of body Electronic Control Unit (ECU) at driver's side of instrument panel and identification of electrical connectors and terminals. See Figure.
  2. Ensure ignition is off. Disconnect body ECU electrical connector 1E and 1J at body ECU. See Figure.
  3. Using voltmeter, check voltage between body ECU electrical connector 1E terminal No. 2 (Blue/Yellow wire) and electrical connector 1J terminal No. 8 (White/Black wire) at body ECU. See Figure. Voltage should be 9-14 volts. If voltage is not within specification, reinstall electrical connectors. Go to next step. If voltage is within specification, reinstall electrical connectors. Go to step  7.
  4. Check DOME fuse (15-amp). DOME fuse is located in fuse/relay box at driver's side front corner of engine compartment. See Figure. If fuse is okay, go to next step. If fuse is defective, repair short in wiring for DOME fuse. See WIRING DIAGRAMS in WARNING SYSTEMS article. For additional wiring for power supply circuit, see POWER DISTRIBUTION article in WIRING DIAGRAMS.
  5. Check wiring harness and electrical connectors between body ECU electrical connector 1J terminal No. 8 (White/Black wire) at body ECU and ground connection. See Figure. See WIRING DIAGRAMS in WARNING SYSTEMS article. If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary and recheck system operation.
  6. Check wiring harness and electrical connectors between battery and body ECU electrical connector 1E terminal No. 2 (Blue/Yellow wire). See WIRING DIAGRAMS . It may be necessary to see WIRING DIAGRAMS in WARNING SYSTEMS article. For additional power supply, see POWER DISTRIBUTION article in WIRING DIAGRAMS. If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary and recheck system operation.
  7. Replace body ECU with a known-good body ECU and recheck system operation. If system operates properly, original body ECU was defective. If system still does not operate properly, check wiring harness and electrical connectors for body ECU for intermittent problem. Repair wiring harness or electrical connector as necessary.
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