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Home >> Lexus >> 1995 >> SC 300 Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Computerized Engine Controls >> ECM Back-Up Power Circuit (Battery)
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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, pull back the right front floor mat. Remove ECM protective cover. Connect Check Harness (09990-01000) between ECM and harness. See USING CHECK HARNESS  under INTRODUCTION.
  2. Measure voltage between chassis ground and terminal No. 33 of ECM connector "A" (Black/Yellow wire). If battery voltage is not present, repair open circuit between ECM and EFI fuse, or between EFI fuse and battery.
  3. If battery voltage is present, check to see if trouble codes remain stored in ECM memory after ignition is turned off. See appropriate TESTS W/CODES article. If trouble codes remain stored, back-up (battery) power circuit is okay. If trouble codes do not remain stored, replace ECM.
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