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Idle Switch Circuit

NOTE: Ensure Throttle Position (TP) sensor adjustment and operation are normal. See appropriate ON-VEHICLE ADJUSTMENTS in ENGINE PERFORMANCE. Adjust or replace TP sensor as necessary.
  1. Remove cruise control ECU with connector attached. Disconnect Engine Control Module (ECM) 28-pin connector "B". See Figure. ECM is located behind glove box. See Figure. Turn ignition on. Measure voltage (backprobe) between ground and terminal No. 13 (Light Green/Red wire) of cruise control ECU connector.
  2. With throttle valve fully open, 10-16 volts should exist. With throttle valve fully closed, less than 1.5 volts should exist. If voltage is not as specified and vehicle is equipped with a V6 engine, go to next step. If voltage is not as specified and vehicle is equipped with a 4-cylinder engine, go to step  4. If voltage is as specified, no problem is indicated at this time. Fault may be intermittent. If sent here from SYMPTOM TESTS , perform next test listed.
  3. Check continuity of Yellow wire between terminal No. 23 of ECM 24-pin harness connector "C" and terminal No. 3 of Throttle Position Sensor (TPS) harness connector. See Figure. Check continuity of Green/Black wire between terminal No. 2 of ECM harness connector "C" and terminal No. 2 of TPS. Check continuity of Light Green wire between terminal No. 18 of ECM harness connector "C" and terminal No. 1 of TPS. Repair as necessary. If wiring and connectors are okay, go to step  6.
  4. Check continuity of Yellow wire between terminal No. 9 of ECM 24-pin harness connector "C" and terminal No. 3 of Throttle Position Sensor (TPS). Check continuity of Green/Yellow wire between terminal No. 2 of ECM harness connector "C" and terminal No. 2 of TPS. Check continuity of Light Green wire between terminal No. 18 of ECM harness connector "C" and terminal No. 1 of TPS. Repair as necessary. If wiring and connectors are okay, go to next step.
  5. Test throttle position sensor circuit. See THROTTLE POSITION SENSOR (TPS) CIRCUIT . If throttle position sensor circuit is okay, test throttle position sensor. See THROTTLE POSITION SENSOR  under COMPONENT TESTS. Replace as necessary. If throttle position sensor is okay, go to next step.
  6. Check wiring harness and connectors between cruise control ECU and ECM. Repair as necessary and retest system. If wiring harness and connectors are okay, replace cruise control ECU and retest system.
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