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Cruise Control Main Switch Circuit

  1. Remove cruise control ECU, leaving electrical connector attached. Turn ignition on. On ES300, measure voltage (backprobe) between cruise control ECU connector terminal No. 11 and ground. See Figure. On RX300, measure voltage (backprobe) between cruise control ECU connector terminal No. 10 and ground.
  2. On all models, with main cruise control switch button released, voltage should be 10-14 volts. With main cruise control switch button pressed, voltage should be less than 0.5 volt. If voltage is not as specified, go to next step. If voltage is as specified, perform next procedure listed in SYMPTOM DIAGNOSIS  table under TROUBLE SHOOTING.
  3. Disable air bag system. See AIR BAG RESTRAINT SYSTEMS article. Remove steering wheel pad. Disconnect electrical connector from cruise control switch. On ES300, check continuity between terminals No. 3 and 5 of cruise control switch connector. See Figure. On RX300, check continuity between terminals No. 4 and 5 of cruise control switch connector.
  4. On all models, with main cruise control switch button released, continuity should not exist. With main cruise control switch button pressed, continuity should exist. If continuity is not as specified, replace cruise control switch. If continuity is as specified, check wiring and connectors between cruise control ECU and cruise control switch. Repair or replace as necessary. If wiring and connectors are okay, check cruise control ECU. See CRUISE CONTROL ECU PIN VOLTAGE TESTS  under COMPONENT TESTS. If cruise control ECU is defective, replace ECU.
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