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Home › Lexus › 2000 › ES 300 › Repair and Diagnosis › Engine Performance › System › Engine Controls - Self-Diagnostics › Diagnostic Tests › DTC P0505: Idle Control System Malfunction › Diagnosis & Repair

Diagnosis & Repair

  1. If using Lexus scan tool, go to next step. If using OBD-II scan tool, go to step  3.
  2. Warm engine to operating temperature. Turn accessories and A/C off. Place transmission in Neutral. Connect Lexus scan tool to DLC No. 3 and select ACTIVE TEST MODE. See Figure. Using Lexus scan tool, turn TE1 on and off. Record engine speed 5 seconds before and after TE1 is turned on and off. If engine speed changes more than 100 RPM, go to step  10. If engine speed does not change more than 100 RPM, go to step  4.
  3. Warm engine to operating temperature. Turn accessories and A/C off. Place transmission in Neutral. Connect OBD-II scan tool to DLC No. 3. Connect Jumper Wire (09843-18020) between DLC No. 1 connector terminals No. 8 (Blue/White wire) and No. 3 (Brown wire). DLC No. 1 is located on front of intake manifold (timing belt side or engine). Connect and disconnect Jumper Wire (09843-18020) several times. Record engine speed 5 seconds before and after Wire Harness (09843-18020) is connected and disconnected. If engine speed changes more than 100 RPM, go to step  10. If engine speed does not change more than 100 RPM, go to next step.
  4. Access ECM behind glove box. Turn ignition off. Disconnect ECM E11 connector. See Figure. Turn ignition on. Using voltmeter, measure voltage between ground and terminal No. 26 (Red/White wire) at ECM E11 connector. If voltage is 9-14 volts, go to step  7. If voltage is not 9-14 volts, go to next step.
  5. Turn ignition off. Disconnect IAC valve harness connector. Measure voltage between ground and terminal No. 2 (Black/Yellow wire) at IAC valve harness connector. If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, repair IAC valve power distribution circuit. See appropriate wiring diagram in WIRING DIAGRAMS article.
  6. Check for open or short in Red/White wire between terminal No. 1 at IAC valve harness connector and terminal No. 26 at ECM harness connector E11. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace IAC valve.
  7. Check IAC system operation. See IDLE CONTROL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, go to next step. If problem does not exist, go to step  9.
  8. Check for open in Brown wire between ground and terminal No. 3 at IAC valve harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace IAC valve.
  9. Check IAC valve and passages for carbon build-up and blockage. Repair as necessary. If no build-up or blockage exists, replace ECM.
  10. Ensure oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem exists, repair as necessary. If problem does not exist, an open or short in A/C switch signal circuit may exist. Check A/C amplifier. See appropriate article in AIR CONDITIONING & HEATING. Repair as necessary.
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