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Test No. 17: Body Electronic Control Unit Does Not Operate

  1. Check AM1 fuse (25-amp), DCC fuse (25-amp), DOOR fuse (20-amp) and MPX-B fuse (7.5-amp). AM1, DOOR and MPX-B fuses are located in instrument panel junction block. See Figure. DCC fuse is located in fuse/relay box at driver's side front corner of engine compartment. See Figure. If fuses are okay, go to next step. If any fuse is defective, repair short in wiring for appropriate fuse. See WIRING DIAGRAMS . For additional wiring for power supply circuit, see POWER DISTRIBUTION article.
  2. Note location of body Electronic Control Unit (ECU). See Figure. Body ECU is located on instrument panel junction block and contains 12-pin, 22-pin and 25 pin electrical connectors. Ensure ignition is off. Disconnect 12-pin electrical connector at body ECU. Using voltmeter, check voltage between terminals No. 5 and 11, and terminals No. 8 and 11 at 12-pin electrical connector for body ECU. See Figure. Voltage should be 10-14 volts. If voltage is not within specification, go to next step. If voltage is within specification, reinstall electrical connector. Go to step  5.
  3. Check wiring harness and electrical connectors between ground connection and terminal No. 11 at 12-pin electrical connector for body ECU. See WIRING DIAGRAMS . If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector are defective, repair as necessary and recheck system operation.
  4. Check wiring harness and electrical connectors between battery and terminals No. 5 and 8 at 12-pin electrical connector for body ECU. See WIRING DIAGRAMS . For additional wiring for power supply circuit, see POWER DISTRIBUTION article. Repair wiring harness or electrical connector as necessary and recheck system operation.
  5. Check body ECU for proper voltage and input signals. See BODY ELECTRONIC CONTROL UNIT  under PIN VOLTAGE TESTS. If proper voltage and input signals exist, go to next step. If proper voltage and input signals do not exist, repair as necessary and recheck system operation.
  6. 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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