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Home >> Toyota >> 2000 >> MR2 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics >> Diagnostic Tests >> DTC P0505: Idle Air Control System Circuit >> Diagnosis & Repair
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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. Note engine RPM. Using a jumper wire, connect terminals No. 4 (White/Black wire) and No. 13 (Pink/Black wire) at Data Link Connector (DLC) No. 3. 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. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 18 (Green wire) at ECM harness connector E5. Voltage should be 9-14 volts. If voltage is not as specified, go to next step. If voltage is as specified, go to step  5.
  3. Turn ignition off. Disconnect IAC valve harness connector. Measure voltage between ground and terminal No. 2 (Black 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 wire between terminal No. 1 at IAC valve harness connector and terminal No. 18 at ECM harness connector E5. 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 - 4-CYLINDER 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. 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. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. Repair as necessary.
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