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HOMESERVICE MANUALSTOYOTA2004CELICA GT, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS (1ZZ-FE) - DIAGNOSTICSDTC TESTS & CIRCUIT INSPECTIONDTC P0505, DTC P0511: IDLE AIR CONTROL SYSTEM, IDLE AIR CONTROL CIRCUITINSPECTION PROCEDUREHAND HELD TESTER
2004 Toyota Celica GT, Standard

Hand held tester

2004 Toyota Celica GT, StandardSECTION Hand held tester
  1. Are there any other codes (besides DTC P0505 and P0511) being output? 

    PREPARATION: 

    1. Connect the hand-held tester to the DLC3.
    2. Turn the ignition switch ON and push the hand-held tester main switch ON.
    3. Enter the following menus: DIAGNOSIS/ENHANCED OBD II/DATA LIST/ALL/MAF.

    CHECK: 

    Read the DTCs.

    RESULT: 

    DISPLAY DTC OUTPUT

    Display (DTC Output) Proceed to
    P0505 and P0511 A
    P0505, P0511 and other DTCs B

    HINT:

    If any other codes besides P0505 and P0511 are output, perform the troubleshooting for those DTCs first.

    1. B : Go to relevant DTC chart (See  DIAGNOSTIC TROUBLE CODE CHART   ). 
    2. A : Go to next step. 
  2. Check connection of PCV piping. 
    1. NG : Repair or replace PCV piping. 
    2. OK : Go to next step. 
  3. Check air induction system. 

    CHECK: 

    Check the air induction system vacuum leaks.

    1. NG : Repair or replace air induction system. 
    2. OK : Go to next step. 
  4. Check engine idle speed. 

    PREPARATION: 

    1. Warm up the engine to the normal operating temperature.
    2. Switch off all the accessories.
    3. Switch off the A/C.
    4. Shift the lever into the neutral position.
    5. Connect the hand-held tester to the DLC3.
    6. Enter the following menus: DIAGNOSIS/ENHANCED OBD II/ACTIVE TEST/ISC DUTY RATIO.

    CHECK: 

    Check that the engine RPM varies when changing the ISC duty ratio.

    OK: 

    Engine PRM fluctuates up and down in response to the ISC duty ratio variation. 

    1. OK : Check for intermittent problems (See  PRE-CHECK   ). 
    2. NG : Go to next step. 
  5. Check A/C signal circuit. 
    1. NG : Repair or replace A/C signal circuit. 
    2. OK : Go to next step. 
  6. Check blockage of IAC valve and passage to bypass throttle valve. 
    1. NG : Replace IAC valve. 
    2. OK : Go to next step. 
  7. Check voltage between terminals VISC and GND of IAC valve connector. 

    PREPARATION: 

    1. Disconnect the IAC valve connector.
    2. Turn the ignition switch ON.

    CHECK: 

    Measure the voltage between the terminals VISC and IAC of IAC valve connector.

    Fig 1: Identifying Terminals VISC And IAC Of IAC Valve Connector
    G02897509Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    OK: 

    Voltage: 9 to 14 V 

    1. NG : Repair or replace harness or connector. 
    2. OK : Go to next step. 
  8. Check for open and short in harness and connector between IAC valve and ECM (See  HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE  ). 
    1. NG : Repair or replace harness or connector. 
    2. OK : Go to next step. 
  9. Check IAC valve (See  Idle Air Control (IAC) Valve  ). 
    1. NG : Replace IAC valve. 
    2. OK : Replace ECM (See  Engine Control Module (ECM)  ). 
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.