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Procedure A, Power Source Circuit

  1. ECU-Ignition Fuse:  Turn ignition switch on, and check Electronic Control Unit-Ignition (ECU-IG) fuse. Replace fuse if blown. If fuse blows after replacing, check wiring harness for a short circuit to ground between fuse and cruise control switch terminal No. 17 (20-pin connector) or ECU terminal No. 12. See Fig 1. If fuse is okay, turn ignition off and go to next step.
  2. Cruise Control Switch:  Disconnect cruise control switch. Check continuity between wiring harness side of cruise control switch terminal No. 17 (20-pin connector) and ground. If continuity exists, go to next step. If no continuity exists, repair open circuit in wire harness between cruise control switch terminal No. 17 (20-pin connector) and ground. Also check for faulty ground.
  3. Check cruise control switch for proper operation. See CRUISE CONTROL SWITCH TEST  under TESTING. If switch is defective, replace switch and recheck cruise control system. If cruise control switch is okay, reconnect switch and go to next step.
  4. Cruise Control ECU:  Disconnect ECU. With MAIN cruise control switch on, check continuity between wiring harness side of ECU terminal No. 6 and ground. If continuity exists, go to next step. If no continuity exists, repair open circuit in wire harness between ECU terminal No. 6 and cruise control switch terminal No. 15 (20-pin connector).
  5. Check continuity between wiring harness side of ECU terminal No. 15 and ground. If continuity exists, go to next step. If no continuity exists, check wiring harness between ECU terminal No. 15 and ground for open circuit. Also check for faulty ground.
  6. Check for battery voltage at wiring harness side of ECU terminal No. 12. If battery voltage is present, go to next step. If no voltage exists, repair open circuit in wire harness to ECU terminal No. 12.
  7. Check GAUGE fuse. Replace fuse if blown. If fuse blows after replacing, check wiring harness for a short circuit between fuse and ECU terminal No. 4. If fuse is okay, go to next step.
  8. Connect wiring harness side of ECU terminal No. 4 to ground. See Fig 1. Observe cruise control indicator light. If cruise control indicator light comes on, replace faulty ECU, and recheck cruise control system.
  9. If cruise control light does not come on, check indicator light bulb. Replace bulb if necessary. If bulb is okay, repair open circuit in wire harness between GAUGE fuse and ECU terminal No. 4.
Fig 1: Cruise Control System Connectors
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