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Home >> Toyota >> 2001 >> Sienna CE >> Repair and Diagnosis >> External Pages >> Different car >> Section 174 (Cruise Control) >> Diagnostic Tests >> DTC 51: Idle Signal Circuit >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Lexus RX 300 and 2002 Lexus RX 300. However, it is still accessible from the selected car via links, so may be relevant.
  1. Remove the cruise control ECU with the connector still connected. Disconnect the ECM connector. Turn the ignition switch ON. Connect the positive (+) lead to terminal No. 13 (IDL) of the cruise control ECU connector and the negative (-) lead to body ground when the throttle valve is fully closed and fully opened. See CONNECTOR IDENTIFICATION . The results are OK if there is 10-14 volts when the throttle valve position is fully opened and below 1.5 volts when the throttle valve position is fully closed. If the results are OK, check the cruise control ECU. If the results are not OK, go to the next step.
  2. Check the wiring harness and connector between the ECM and throttle position sensor. If the results are OK, go to the next step. If the results are not OK, repair or replace the wiring harness or connector.
  3. Check the throttle position sensor circuit. If the results are OK, go to the next step. If the results are not OK, replace the throttle position sensor. See THROTTLE BODY under FUEL SYSTEM under REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE.
  4. Check for an open and short in the wiring harness and connector between the cruise control ECU and ECM. If the results are OK, check and replace the cruise control ECU. See CRUISE CONTROL ECU  under REMOVAL & INSTALLATION. If the results are not OK, repair or replace the wiring harness or connector.
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