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Home >> Mazda >> 2001 >> B2500 SE, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> System Tests >> Test HY: Generator/Regulator System >> Diagnostic Aids
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Diagnostic Aids

Perform this test when directed by QUICK TEST. This test is intended to diagnose the following:

  1. 1) KOER & Continuous Memory DTC P1246: Verify Generator Drive Function

    This DTC is set when PCM detects voltage regulator temperature (calculated generator load frequency) falls below 6 percent. Possible causes are:
    • Generator Circuit Open, Or Shorted To GND Or PWR
    • FaultyGenerator Drive Mechanism
    • Faulty Generator/Regulator Assembly
    • Faulty PCM

    Check generator drive belt condition and tension. Start engine and verify generator is turning. Repair as necessary. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If no faults are found, go to next step.

  2. 2) Verify Charging System Is EEC Controlled

    Turn ignition switch to OFF position. Disconnect negative then positive battery cable. Disconnect generator connector. Using a DVOM, measure resistance between generator harness connector BATT-SENSE and GEN-COM terminals. See Fig 1. If resistance is 950-1050 ohms, go to next step. If resistance is not 950-1050 ohms, replace generator/regulator assembly.
    Fig 1: Identifying Generator Wiring Harness Connector Terminals (Tribute 2.0L)
    G00013291Courtesy of FORD MOTOR CO.

  3. 3) Check Battery Sense Voltage At Battery

    Reconnect generator connector. Reconnect battery cables to battery. Using a DVOM, measure voltage between battery terminals. Note voltage measurement. Using a DVOM, measure voltage between negative battery terminal and generator harness connector BATT-SENSE terminal. If voltage is within .5 volt (plus or minus) of battery voltage measurement, go to next step. If voltage is not within .5 volt of battery voltage measurement, repair BATT-SENSE circuit as necessary.

  4. 4) Check Generator Failure Mode

    Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Ensure all accessories are off. Using scan tool, access GFSF PID from PID/DATA MONITOR & RECORD menu. Start engine and raise engine speed to 2000 RPM. Note GFSF PID value. Wiggle and bend wiring harness between generator and PCM. Fault is indicated by a change in GFSF PID value. If a fault is indicated, go to next step. If no fault is indicated, check charging system and repair as necessary. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS.

  5. 5) Check GEN-MON & GEN-COM Circuits For Short To PWR

    Turn ignition switch to OFF position. Disconnect PCM connector(s). Disconnect generator connector. Turn ignition switch to ON position. Using a DVOM, measure voltage between negative battery terminal and PCM harness connector GEN-COM and GEN-MON terminals. See Fig 1. If both voltage measurements are .5 volt or less, go to next step. If either voltage measurement is more than .5 volt, repair short to PWR in affected GEN-COM or GEN-MON circuit.

  6. 6) Check GEN-COM & GEN-MON Circuits For Short To GND

    Turn ignition switch to OFF position. Using a DVOM, measure resistance between negative battery terminal and PCM harness connector GEN-COM and GEN-MON terminals. If both resistance measurements are more than 10 k/ohms, go to next step. If either resistance measurement is 10 k/ohms or less, repair short to GND in affected GEN-COM or GEN-MON circuit.

  7. 7) Check GEN-COM & GEN-MON Circuits For Open

    Using a DVOM, measure resistance of GEN-COM and GEN-MON circuits between PCM harness connector and generator harness connector. If both resistance measurements are less than 5 ohms, go to next step. If either resistance measurement is 5 ohms or more, repair open in affected GEN-COM or GEN-MON circuit.

  8. 8) Check GEN-MON Signal

    Reconnect all connectors. Start engine and allow to idle. Using scan tool, access GFS PID from PID/DATA MONITOR & RECORD menu. If GFS PID duty cycle is 6-98 percent, go to next step. If GFS PID duty cycle is not 6-98 percent, replace generator/regulator assembly.

  9. 9) Check GEN-COM Signal

    With engine idling, access GENFDC PID from PID/DATA MONITOR & RECORD menu. Observe ALTFDC or GENFDC PID value, while turning headlights on and off. If ALTFDC or GENFDC PID duty cycle reading switched from zero to 99 percent, fault is unable to be duplicated at this time. Go to TEST Z, step  1). If ALTFDC or GENFDC PID duty cycle reading did not switch from zero to 99 percent, replace PCM.
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