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Home >> Lexus >> 1997 >> SC 400 >> Repair and Diagnosis >> External Pages >> Different car >> Section 11 (Cruise Control System) >> Circuit Testing >> Test 8: Ecu Power Source Circuit
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Test 8: Ecu Power Source Circuit

WARNING: This page is about a different car, the 1997 Lexus SC 300. However, it is still accessible from the selected car via links, so may be relevant.

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. If battery voltage is present, perform next procedure listed in DIAGNOSIS BY SYMPTOM  table under TROUBLE SHOOTING. If battery voltage is not present, measure resistance between ground and terminal No. 13 of cruise control ECU connector.
  3. 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.
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