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Home >> Mazda >> 2002 >> Tribute LX, 4WD >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P1474, DTC P1477 Or DTC P1479 >> Diagnostic Procedures

Diagnostic Procedures

  1. If QUICK TEST was not performed, go to QUICK TEST  under SELF-DIAGNOSTIC SYSTEM. If QUICK TEST was performed, proceed as follows:
    • If DTC P1474 is present, go to step  10.
    • If DTC P1477 is present, go to step  12.
    • If DTC P1479 is present, go to step  14 (for 2.0L) or go to step  7 (for 3.0L).

    For all others, go to next step.

  2. Check VPWR (IGN START/RUN) Voltage To Applicable Fan Relay

    Disconnect appropriate fan control relay:
    • DTC 1474: LFC
    • DTC 1477: MFC
    • DTC 1479: HFC

    Turn ignition on, engine off. Measure VPWR (IGN START/RUN) circuit voltage at applicable fan control relay harness connector. See WIRING DIAGRAMS article. If voltage reading is more than 10.5 volts, go to next step. If voltage reading is not as specified, repair open in VPWR (IGN START/RUN) circuit to applicable fan control relay. After repair, go to step  16.

    NOTE: Commanding LFC PID on will also command MFC PID output on if MFC PID is not available.

  3. Check For LFC, MFC Or HFC Circuit Cycling

    Connect a non-powered test light between VPWR circuit (White/Violet wire) and LFC, MFC or HFC circuit at the applicable fan control relay 5-pin harness connector. See WIRING DIAGRAMS article. Using scan tool, select DIAGNOSTIC DATA LINK. Select PCM. Select ACTIVE COMMAND MODES. Select OUTPUT TEST MODE. While observing test light, command appropriate cooling fan (LFC, MFC or HFC PIDs) speed on and off. If test light does not turn on and off when cooling fan output is commanded on and off, repeat test to verify results. If test results are same, remove testlight. Turn ignition off and go to next step. If test light turns on and off when cooling fan output is commanded on and off, replace appropriate fan control relay. After repair, go to step  16.

  4. Check LFC, MFC Or HFC Circuit For Short To Power In Harness

    Disconnect PCM 104-pin harness connector. Turn ignition on, engine off. Measure voltage between ground and LFC, MFC or HFC circuit at applicable fan relay 5-pin harness connector. If voltage reading is less than one volt, go to next step. If voltage reading is not as specified, repair short to power between PCM 104-pin harness connector and appropriate fan control relay 5-pin harness connector. After repair, go to step  16.

  5. Check LFC Or HFC Circuit For Short To Ground In Harness

    Turn ignition off. Disconnect scan tool. Measure resistance between ground and LFC, MFC or HFC circuit at applicable fan control relay harness connector. If resistance reading is more than 10,000 ohms, go to next step. If resistance reading is not as specified, repair short circuit between PCM 104-pin harness connector and appropriate fan control relay. After repair, go to step  16.

  6. Check For Open LFC, MFC Or HFC Circuit

    Connect Breakout Box (49-UN01-130) to PCM harness connector only. See Figure. Measure resistance of LFC, MFC or HFC circuit between breakout box terminal and appropriate fan control relay harness connector.
    • LFC - breakout box terminal No. 68 (2.0L) or No. 28 (3.0L).
    • MFC - breakout box terminal No. 43 (2.0L) or No. 42 (3.0L).
    • HFC - breakout box terminal No. 17 (2.0L) or No. 46 (3.0L).

    If resistance reading is less than 5.0 ohms, replace PCM. After repair, go to step  16. If resistance reading is not as specified, repair open circuit between PCM 104-pin harness connector and appropriate fan control relay terminal No. 2.

  7. Check Ignition START/RUN Circuit Voltage To High Speed FC Relay No. 1

    Disconnect HFC relay No. 1 (MAIN FAN relay in battery junction box). Turn ignition on, engine off. Measure VPWR (IGN START/RUN) circuit voltage at applicable fan control relay 5-pin harness connector (White Violet wire). See WIRING DIAGRAMS article. If voltage reading is more than 10.5 volts, go to next step. If voltage reading is not as specified, repair open in IGN START/RUN circuit (White/Violet wire) between PCM power relay and HFC relay No. 1. After repair, go to step  16.

  8. Check For HFC Circuit Cycling At High Speed FC Relay No. 1

    Connect a non-powered test light between VPWR circuit and LFC, MFC or HFC circuit at applicable fan control relay 5-pin harness connector. Using scan tool, select DIAGNOSTIC DATA LINK. Select PCM. Select ACTIVE COMMAND MODES. Select OUTPUT TEST MODE. While observing test light, command high speed cooling fan on and off (using HFC PID). If test light turns on and off when cooling fan output is commanded on and off, replace HFC relay No. 1. After repair, go to step  16. If test light does not turn on and off when cooling fan output is commanded on and off, leave test light connected and go to next step.

  9. Check For HFC Circuit Cycling With High Speed FC Relay No. 2 Disconnected

    Disconnect HFC relay No. 2 (ADD FAN relay in battery junction box). While observing test light, command high speed cooling fan on and off (using HFC PID). If test light turns on and off when cooling fan output is commanded on and off, replace HFC relay No. 2. After repair, go to step  16. If test light does not turn on and off when cooling fan output is commanded on and off, go to step  4 to diagnose HFC circuit. Make checks at HFC relay No. 1 5-pin harness connector.

  10. Check Low Speed Fan Control (LFC) Circuit For Open Or Short To Power

    Verify A/C and defrost are off. Disconnect cooling fan 3-pin harness connectors. Connect a non-powered test light between (LOW) FAN PWR circuit (Gray/Red wire) and ground circuit at cooling fan 3-pin harness connector. Toggle load on and off (headlights).
    • For 2.0L, use driver's side fan.
    • For 3.0L, use passenger's side fan.

    Turn ignition on, engine off. Using scan tool, select DIAGNOSTIC DATA LINK. Select PCM. Select ACTIVE COMMAND MODES. Select OUTPUT TEST MODE. Command LOW SPEED FAN on (using LFC PID). Observe test light for an indication of a fault while completing following (the lamp will turn off when a fault is detected, indicating an open or short to power):

    • Shake, wiggle and bend LFC circuit between PCM and LFC relay.
    • Shake, wiggle and bend VPWR (IGN START/RUN) circuit to LFC relay.
    • Lightly tap on LFC relay to simulate road shock.

    If no fault is indicated, go to next step. If a fault is indicated, isolate fault and repair as necessary. After repair, go to step  16.

  11. Check LFC Circuit For Short To Ground

    Command LFC relay off (using LFC PID). Observe test light for an indication of a fault while completing following (test lamp will turn on when a fault is detected, indicating LFC circuit short to ground):
    • Shake, wiggle and bend the LFC circuit between the PCM and low speed FC relay.
    • Lightly tap on the low speed FC relay to simulate road shock.

    If a fault is indicated, isolate fault and repair as necessary. After repair, go to step  16. If a fault is not indicated, fault is intermittent. Refer to INTERMITTENT  testing under SYSTEM TESTING.

  12. Check Medium Speed Fan Control (MFC) Circuit For Open Or Short To Power

    Verify A/C and defrost are off. Disconnect cooling fan 3-pin harness connectors. Connect a non-powered test light:
    • For 2.0L, connect test light between MEDIUM FAN PWR circuit (Light Blue/Black wire) and ground circuit at passenger-side cooling fan 3-pin harness connector.
    • For 3.0L, disconnect MFC relay (located on left front of radiator core support) and connect test light between MFC circuit (Black wire) and IGN START/RUN circuit (White/Violet wire) at MFC relay 5-pin harness connector.
    NOTE: Commanding LFC PID on will also command MFC PID output on if MFC PID is not available.

    Turn ignition on, engine off. Using scan tool, select DIAGNOSTIC DATA LINK. Select PCM. Select ACTIVE COMMAND MODES. Select OUTPUT TEST MODE. Command medium speed fan on (using LFC or MFC PID). Observe test light for an indication of a fault while completing following (lamp will turn off when a fault is detected, indicating an open or short to power):

    • Shake, wiggle and bend MFC circuit between PCM and MFC relay.
    • Shake, wiggle and bend VPWR (IGN START/RUN) circuit to MFC relay.
    • For 2.0L, lightly tap on MFC relay to simulate road shock.

    If a fault is not indicated, go to next step. If a fault is indicated, isolate fault and repair as necessary. After repair, go to step  16.

  13. Check MFC Circuit For Short To Ground

    Command low speed fan off (using LFC or MFC PID). Observe test light for an indication of a fault while completing following (lamp will turn on when a fault is detected, indicating MFC circuit short to ground):
    • Shake, wiggle and bend MFC circuit between PCM and MFC relay.
    • For 2.0L, lightly tap on MFC relay to simulate road shock.
    • For 3.0L, inspect MFC relay for intermittent concerns.

    If a fault is indicated, isolate fault and repair as necessary. After repair, go to step  16. If a fault is not indicated, problem is intemittent. Refer to INTERMITTENT  testing under SYSTEM TESTS .

  14. Check High Speed Fan Control (HFC) Circuit For Open Or Short To Power

    Verify A/C and defrost are off. Disconnect cooling fan 3-pin harness connectors. Connect a non-powered test light between (HIGH) FAN PWR circuit and ground circuit at cooling fan harness connector. For 2.0L, use driver's side fan. For 3.0L, use passenger's side fan. Turn ignition on, engine off. Using scan tool, select DIAGNOSTIC DATA LINK. Select PCM. Select ACTIVE COMMAND MODES. Select OUTPUT TEST MODE. Command high speed fan on (using HFC PID). Observe test light for an indication of a fault while completing following (lamp will turn off when a fault is detected, indicating an open or short to power):
    • Shake, wiggle and bend HFC circuit between PCM and HFC relay.
    • Shake, wiggle and bend VPWR (IGN START/RUN) circuit to HFC relay.
    • Lightly tap on HFC relay to simulate road shock.

    If a fault is not indicated, go to next step. If a fault is indicated, isolate fault and repair as necessary. After repair, go to step  16.

  15. Check HFC Circuit For Short To Ground

    Command high speed fan off (using HFC PID). Observe test light for an indication of a fault while completing following (lamp will turn on when a fault is detected, indicating HFC circuit short to ground):
    • Shake, wiggle and bend HFC circuit between PCM and HFC relay.
    • Lightly tap on HFC relay to simulate road shock.

    If a fault is not indicated, replace generator/regulator assembly. After repair, go to next step. If fault is indicated, isolate fault and repair as necessary. After repair, go to next step.

  16. 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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