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Home >> Toyota >> 2001 >> Avalon XLS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics >> Diagnostic Tests >> DTC P0505: Idle Air Control System Circuit >> Diagnosis & Repair

Diagnosis & Repair

  1. Start engine and warm to normal operating temperature. Turn all accessories off. Ensure A/C is off. Shift transaxle lever into Neutral. Connect scan tool to Data Link Connector (DLC) No. 3. See Figure. Note engine RPM. Using a jumper wire, connect terminals TE1 and E1 at DLC No. 1 in engine compartment. See Fig 1. Note engine RPM and compare RPM readings. If difference in engine speed is 100 RPM or less, go to next step. If difference in engine speed is more than 100 RPM, go to step  7.
  2. Turn ignition off. Disconnect ECM harness connector E4. Turn ignition on. Measure voltage between ground and terminal No. 26 (Green/Black wire) at ECM harness connector E4. See Figure. If voltage is not 9-14 volts, go to next step. If voltage is 9-14 volts, go to step  5.
  3. Turn ignition off. Disconnect IAC valve harness connector. Measure voltage between ground and terminal No. 2 (Black/White 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 WIRING DIAGRAMS article.
  4. Check for open or short in Green/Black wire between terminal No. 1 at IAC valve harness connector and terminal No. 26 at ECM harness connector E4. See WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace IAC valve.
  5. Check IAC valve operation. See IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING - V6 & V8 article. If problem does not exist, go to next step. If problem exists, repair as necessary.
  6. Remove IAC valve from throttle body. Check IAC valve and passages for carbon build-up and blockage. If problem exists, repair or replace as necessary. If problem does not exist, replace ECM.
  7. 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 signal circuit may exist. Check A/C signal circuit. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. Repair as necessary.
Fig 1: Installing Jumper Wire Between DLC No. 1 Terminals
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