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ECM Back-Up Power Circuit (Battery)

  1. Check EFI fuse. See COMPONENT LOCATIONS  under INTRODUCTION. If EFI fuse is blown, repair circuit. If EFI fuse is okay, remove cover from below right side of instrument panel for access to ECM. Measure voltage between chassis ground and terminal No. 14 (Black/Yellow wire) of ECM connector E12. To identify ECM connectors and terminals, see Figure.
  2. If battery voltage is not present, repair circuit between ECM and EFI fuse, or between EFI fuse and battery. If battery voltage is present, check to see if trouble codes remain stored in ECM memory after ignition is turned off. See TESTS W/CODES - EXCEPT OBD-II article in the ENGINE PERFORMANCE section. If trouble codes remain stored, back-up power circuit is okay. If trouble codes do not remain stored, replace ECM.
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