1996 Lexus SC 400FACTORY OEM SERVICE PROCEDURE

Test 8 (Ecu Power Source Circuit)

Cruise control ECU power source circuit supplies power to actuator and sensors. Cruise control ECU is grounded internally (through the case) and externally (through a ground wire).

  1. Check ECU-IG fuse, located under left side of instrument panel, in junction block No. 1. If fuse is blown, repair short circuit. If fuse is okay, remove cruise control ECU, but leave electrical connector(s) attached.
  2. Turn ignition on. Measure voltage between terminals no. 14 (+) and 13 (-) of cruise control ECU connector. See Figure.
  3. If battery voltage is present, perform next procedure listed in DIAGNOSIS BY SYMPTOMΒ  table. If battery voltage is not present, measure resistance between ground and terminal no. 13 of cruise control ECU connector. See Figure.
  4. If resistance is one ohm or more, repair circuit between cruise control ECU and ground. If resistance is less than one ohm, repair circuit between battery and cruise control ECU.
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.

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