LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Toyota >> 2003 >> Matrix Base, FWD, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 13 (Engine Control System Self-Diagnostics - V6) >> Diagnostic Tests >> DTC P0505: Idle Air Control System Circuit >> Diagnosis & Repair
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Diagnosis & Repair

WARNING: This page is about a different car, the 2002 Toyota Highlander. However, it is still accessible from the selected car via links, so may be relevant.
  1. Start engine and warm to normal operating temperature. Turn all accessories off. Ensure A/C is off. Shift transaxle lever into Neutral. Note engine RPM. Using a jumper wire, connect terminals 13 (Pink/Black wire) and No. 4 (White/Black wire) at DLC No. 3 under dash. See Figure. 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. Remove jumper wire. Disconnect IAC valve harness connector. Turn ignition on. Measure voltage between ground and terminal No. 2 (Black/White wire) at IAC valve harness connector. See Fig 1. If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, repair wiring between IAC valve and EFI relay. See WIRING DIAGRAMS article.
  3. Turn ignition off. Check continuity between ground and terminal No. 3 (Black/White wire) at IAC valve harness connector. If continuity exists, go to next step. If continuity does not exist, repair open in Black/White wire between IAC valve and ground. See WIRING DIAGRAMS article.
  4. Access ECM behind glove box. See Figure. Disconnect ECM harness connector E9. See Figure. 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 E9. If problem does not exist, go to next step. If problem exists, repair wiring as necessary.
  5. Connect all disconnected components. 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, replace IAC valve.
  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. Remove jumper wire. 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 MANUAL HIGHLANDER or AUTOMATIC HIGHLANDER A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. Repair as necessary.
Fig 1: Identifying IAC Valve Harness Connector Terminals
G95G31381Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
scientia non olet · About LEMON Manuals