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Home >> Mazda >> 2002 >> Tribute LX, 4WD >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0505, DTC P1504 Or DTC P1507 >> Diagnostic Procedures

Diagnostic Procedures

  1. If QUICK TEST was not performed, go to QUICK TEST  under SELF-DIAGNOSTIC SYSTEM. If QUICK TEST was performed, go to next step.
    NOTE: If EGR DTC P0402 was present during Self-Test, diagnose it first before continuing with next test.

  2. DTC P0505, P1504, P1507 Or Starts Only At Part Throttle: Check VPWR To IAC Valve Assembly

    Disconnect IAC valve. Turn ignition on, engine off. Measure voltage between ground and VPWR terminal (White/Red wire) at IAC valve harness connector. Turn ignition off. If voltage reading was more than 10.5 volts, go to next step. If voltage reading was not as specified, repair open in White/Red wire between PCM 104-pin harness connector terminals No. 71 and 97 and IAC valve harness connector. See WIRING DIAGRAMS article. After repair, go to step  12.
    NOTE: Due to diode in solenoid, place DVOM positive lead on VPWR terminal and negative lead on IAC terminal.

  3. Check IAC Valve Resistance

    Measure IAC valve assembly resistance. If resistance is 6-13 ohms, go to next step. If resistance reading is not as specified, replace IAC valve assembly. After repair, go to step  12.

  4. Check IAC Valve Assembly For An Internal Short To IAC Case

    Measure resistance from IAC terminal to IAC valve case. See Fig 1. If resistance reading is more than 10,000 ohms and DTC P1504 is present, go to step  7. For all other DTCs, go to next step. If resistance reading is not as specified, replace IAC valve. After repair, go to step  12.
    Fig 1: Identifying IAC Valve Circuit & Harness Connector Terminals
    G00158999Courtesy of MAZDA MOTORS CORP.

  5. Check Air Inlet For Plugging

    Inspect entire air intake system for debris, blockage and other damage. Remove and inspect air cleaner element for excessive dirt. If air intake system is okay, restore air inlet system and go to next step. If problem is found in air intake system, repair as necessary. After repair, go to step  12.

  6. Check For Vacuum Leaks

    Start engine. With engine running at idle, listen for vacuum leaks. Inspect entire air intake system from Mass Airflow (MAF) sensor to intake manifold for leaks such as:
    • Cracked or punctured intake air tube.
    • Loose intake air tube at air cleaner housing or throttle body.
    • IAC valve assembly or gasket seal.
    • EGR valve gasket seal.
    • Vacuum supply connector and hose.
    • PCV connectors and hose.

    Turn ignition off. If no leaks were detected, go to next step. If any leaks were detected, repair as necessary. After repair, go to step  12.

  7. Check IAC Circuit Resistance

    Disconnected PCM and IAC valve harness connectors. Connect Breakout Box (49-UN01-130) to PCM harness connector only. See Figure. Measure resistance of IAC circuit (White/blue wire) between breakout box terminal No. 83 and IAC valve harness connector. Is resistance reading is less than 5.0 ohms, go to next step. If resistance reading is not as specified, repair open in White/Blue wire between PCM 104-pin harness connector terminal No. 83 and IAC valve harness connector. See WIRING DIAGRAMS article. After repair, go to step  12.

  8. Check IAC Circuit For Short To PWR

    Turn ignition on, engine off. Measure voltage between ground and breakout box terminal No. 83 (IAC). Turn ignition off. If voltage reading was less than one volt, go to next step. If voltage reading was not as specified, repair short in White/Blue wire between PCM 104-pin harness connector terminal No. 83 and IAC valve harness connector. After repair, go to step  12.

  9. Check IAC Circuit For Short To Ground

    Disconnect scan tool from DLC. Measure resistance between breakout box terminals No. 83 (IAC) and No. 103 (PWR GND). If resistance reading is more than 10,000 ohms, go to next step. If resistance reading is 10,000 ohms or less, repair short in White/Blue wire between PCM 104-pin harness connector terminal No. 83 and IAC valve harness connector. After repair, go to step  12.
    NOTE: During following step, if stalling occurs, place a shim under the hard stop screw to maintain idle conditions.
    NOTE: If closed throttle RPM is significantly higher than normal, ignore next step.

  10. Check IAC Signal From PCM

    Remove Breakout Box. Reconnect PCM and IAC valve harness connectors. Reconnect scan tool. Start engine. Using scan tool, select DIAGNOSTIC DATA LINK. Select PCM Select PID DATA MONITOR AND RECORD. Access IAC and RPM PIDs. With engine at normal operating temperature, all accessories off and at closed throttle, IAC duty cycle must be approximately 22-45 percent. Slowly increase engine speed to 3000 RPM and return to closed throttle. If IAC duty cycle is within specification at closed throttle and duty cycle responded to change in RPM, proceed as follows:
    • For DTCs P1504 and P1507, go to next step.
    • For all other DTCs, turn ignition off. Inspect throttle body for damage. Repair as necessary. If throttle body is okay, replace IAC valve. After repair, go to step  12.

    If IAC duty cycle is not within specification at closed throttle and duty cycle does not responded to change in RPM, proceed as follows:

    • For DTC P1507, replace IAC valve.
    • For all other DTCs, replace PCM.

    After repair, go to step  12.

  11. Check IAC System For Intermittent Open Or Short

    Using scan tool, select DIAGNOSTIC DATA LINK. Select PCM. Select PID DATA MONITOR AND RECORD. Access IAC and RPM PIDs. Observe PIDs for an indication of a fault while performing the following at idle:
    • Lightly tap on IAC valve and wiggle harness connector to simulate road shock.
    • Grasp vehicle harness closest to IAC valve. Shake and bend a small section of harness from IAC valve to dash panel and from dash panel to PCM.

    If IAC and RPM PIDs suddenly change in value indicating a fault, isolate fault and repair as necessary. After repair, go to next step. If IAC and RPM PIDs do not suddenly change in value and idle quality, starting or stalling symptoms currently present, replace IAC valve. After repair, go to next step. For all other concerns, problem is intermittent. Refer to INTERMITTENT  testing under SYSTEM TESTS .

  12. Verify Trouble Shooting Of DTCs Completed

    Reconnect all disconnected connectors. Clear DTCs from PCM memory using scan tool. Perform QUICK TEST  under SELF-DIAGNOSTIC SYSTEM. If same DTC is present, replace faulty PCM. Repeat QUICK TEST  under SELF-DIAGNOSTIC SYSTEM. If same DTC is not present, go to applicable procedure for other DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are present, trouble shooting is complete.
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