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Test 4: Electronic Fuel Injection Communication Circuit

WARNING: This page is about a different car, the 1997 Lexus SC 400. However, it is still accessible from the selected car via links, so may be relevant.
  1. Remove cruise control ECU, but leave electrical connector(s) attached. Warm engine to normal operating temperature. Connect voltmeter between ground and terminal No. 6 of cruise control ECU connector. See Figure.
  2. Drive vehicle. When driving downhill, voltage should be less than one volt. When driving uphill, voltage should be 8-14 volts. If voltage is as specified, perform next procedure listed in DIAGNOSIS BY SYMPTOM  table under TROUBLE SHOOTING.
  3. If voltage is not as specified, check for faulty circuit between cruise control ECU and engine/transmission ECM. Repair circuit if necessary. If circuit is okay, replace cruise control ECU.
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