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Home >> Mazda >> 2002 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 48 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0300, DTC P0301, DTC P0302, DTC P0303, DTC P0304, DTC P0305 Or DTC P0306 >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Mazda B4000, 2002 Mazda B3000, and 2002 Mazda B2300. However, it is still accessible from the selected car via links, so may be relevant.
  1. If QUICK TEST was not performed, go to QUICK TEST  under SELF-DIAGNOSTIC SYSTEM. If QUICK TEST was performed:
    • For DTC P0300 only, go to step  18 .
    • For all others, go to next step.

  2. Check/Compare PID Values

    Verify all electrical accessories are off. With KOEO, access DPFEGR PID and record values. With KOER, observe DPFEGR PID and record values. Turn ignition off. Compare KOEO values with KOER values. Calculate difference in values by subtracting KOEO values from KOER values. If value difference is within 0.15 volts, go to step  4 . If value difference is not within 0.15 volts, go to next step.
    NOTE: Perform KOER Self-Test and repair any DTCs before proceeding with next step.

  3. Check Operation Of EGR Valve

    Misfire symptom indicates possible EGR flow at idle with no EGR DTCs set. Possible causes are:
    • EGR valve not fully seating.
    • EGR vacuum regulator solenoid vent restricted.
    • Damaged EGR vacuum regulator solenoid.
    Disconnect and plug vacuum hose at EGR valve. With KOEO, access DPFEGR PID and record voltage. With KOER, access DPFEGR PID and record voltage. Turn ignition off. Compare KOEO values with KOER values. An increase in voltage at idle indicates DPFEGR sensor is sensing EGR flow. If DPFEGR PID value is greater at idle by a minimum of 0.15 volts than with engine off, DPFEGR PID voltage is indicating EGR flow at idle. Since EGR vacuum hose is disconnected and plugged, problem is most likely a faulty EGR valve. Remove and inspect EGR valve. Repair or replace EGR valve as necessary. Go to step  20 . If DPFEGR PID value is not greater at idle by a minimum of 0.15 volts than with engine off, this indicates a fault in EGR valve vacuum supply. Inspect EGR vacuum regulator (EGRVR) solenoid vent and vent filter for restrictions. Repair as necessary. If solenoid vent and vent filter are okay, replace faulty EGRVR solenoid. Go to step  20 .

  4. Check Fuel Pressure

    Release fuel pressure. Install fuel pressure gauge. With KOER, record fuel pressure. Increase engine speed to 2500 RPM and maintain increased engine speed for one minute. Record fuel pressure. Turn ignition off. Compare recorded fuel pressures. Fuel pressure must be within 5 psi of specification and maintained for 60 seconds. See FUEL PRESSURE SPECIFICATIONS  table. If fuel pressure is within 5 psi of specification for 60 seconds, go to next step. If fuel pressure is not within 5 psi of specification for 60 seconds, see FUEL DELIVERY SYSTEM  under SYSTEM TESTS.
    FUEL PRESSURE SPECIFICATIONS

    Engine psi (kPa)
    2.3L 35-55 (240-380)
    3.0L & 4.0L 30-65 (207-448)

  5. Check Injector Driver PIDs INJ1F Through INJ6F

    With KOEO, access suspect injector PID. If injector PID status is YES, go to next step. If injector PID status is not YES, go to step  9 .

  6. Check Resistance Of Fuel Injector(s) & Harness

    Turn ignition off. Disconnect PCM connector. Install breakout box, leaving PCM disconnected. Measure resistance of suspect INJ circuit between breakout box terminal No. 71 (VPWR circuit) and suspect fuel injector breakout box terminal. See INJ CIRCUIT IDENTIFICATION  . See Fig 1 . If resistance is 11-13 ohms (2.3L), 8.5-15.5 ohms (3.0L) or 11-18 ohms (4.0L), replace faulty PCM. Go to step  20 . If resistance is not 11-13 ohms (2.3L), 8.5-15.5 ohms (3.0L) or 11-18 ohms (4.0L), go to next step.
    INJ CIRCUIT IDENTIFICATION

    Injector Breakout Box Terminal Wire Color
    Injector 1 No. 75 Tan
    Injector 2 No. 101 White
    Injector 3 No. 74 Brown/Yellow
    Injector 4 No. 100 Brown/Light Blue
    Injector 5 No. 73 Tan/Black
    Injector 6 No. 99 Light Green/Orange
    Fig 1: Fuel Injector Harness Connector Circuit Identification
    G00155536Courtesy of MAZDA MOTORS CORP.

  7. Check Resistance Of Fuel Injector Harness

    Disconnect suspect injector harness connector. Measure resistance of VPWR circuit between breakout box terminal No. 71 or 97 and fuel injector harness connector. Record reading. See Fig 1 . Measure resistance of INJ circuit between appropriate breakout box terminal and suspect fuel injector breakout box terminal. See INJ CIRCUIT IDENTIFICATION  table. Record reading. If each resistance reading is less than 5 ohms, go to next step. If each resistance reading is 5 ohms or more, repair open circuit. See WIRING DIAGRAMS article. Go to step  20 .

  8. Check Fuel Injector Harness Circuit For Short To Power Or Ground

    Measure resistance between suspect INJ circuit breakout box terminal and breakout box terminal No. 71 (VPWR circuit). See Fig 1 . For INJ circuit identification, see INJ CIRCUIT IDENTIFICATION  table. Record reading. Measure resistance between suspect INJ circuit breakout box terminal and breakout box terminal No. 103 (PWR GND circuit). Record reading. If each resistance reading is more than 10,000 ohms, go to next step. If each resistance reading is 10,000 ohms or less, repair short circuit. See WIRING DIAGRAMS article. Go to step  20 .

  9. Inspect Fuel Injector Operation

    Remove suspect fuel injector from engine. Switch suspected fuel injector with a fuel injector from another cylinder. With KOER, observe engine running condition. If misfire moved to cylinder with suspect fuel injector, replace faulty fuel injector. Go to step  20 . If misfire did not move to cylinder with suspect fuel injector, go to next step.

  10. Check Vacuum System

    Inspect vacuum lines for damage and proper routing. If vacuum lines are okay, go to next step. If vacuum lines are not okay, repair as necessary. Go to step  20 .

  11. Check Damper & Pulley Assembly

    Observe crankshaft pulley for wobble. Examine pulse ring fastened to harmonic damper. If component conditions are okay, go to next step. If crankshaft pulley wobbles or pulse ring is loose or damaged, replace damper or pulse ring. Disconnect vehicle battery for 5 minutes to allow PCM to learn new data (due to old pulse ring). After repair, go to step  20 .
    NOTE: Misfire Monitor can be influenced by Evaporative Emission (EVAP) system. Next five test steps will diagnose EVAP system.

  12. Check Evaporative Emission System

    Inspect EVAP canister for fuel saturation. If an excess amount of liquid fuel is present, replace EVAP canister. Go to step  20 . If an excess amount of liquid fuel is not present, check fuel tank vent system. Go to next step.

  13. Pressure Test EVAP Emission System

    Perform an EVAP emission system leak test. See EVAPORATIVE EMISSIONS SYSTEM LEAK TEST under SYSTEM TESTS (EVAPORATIVE EMISSION) in SYSTEM & COMPONENT TESTING - B2300, B3000, B4000 & TRIBUTE article. If EVAP system is holding pressure, go to next step. If EVAP system is leaking, repair as necessary. Go to step  20 .

  14. Check Vacuum In EVAP Emission System

    Inspect EVAP hoses between engine vacuum port and EVAP canister for blockage and cut hoses. Inspect fuel tank vent hoses for blockage. If a fault is located, replace or repair vacuum hoses as necessary. Go to step  20 . If a fault is not located, go to next step.

  15. Check For EVAP Emission Purge Valve Housing Leaks

    Verify EVAP purge solenoid is electrically connected. Disconnect vacuum line between EVAP purge solenoid and intake manifold at solenoid. Connect a hand vacuum pump to EVAP purge solenoid nipple. Apply 16 in. Hg (53 kPa) of vacuum to EVAP purge solenoid. Observe vacuum pump. If EVAP purge solenoid holds vacuum (at room temperature), go to next step. If EVAP purge solenoid does not hold vacuum (at room temperature), replace faulty EVAP purge solenoid. Go to step  20 .

  16. Check For Filter Contamination Or Damage On Evaporative Emission Purge Valve

    Disconnect vacuum line between EVAP purge solenoid and intake manifold at solenoid. Connect a hand vacuum pump to EVAP purge solenoid nipple. Apply 10-15 in. Hg (48-52 kPa) of vacuum to EVAP purge solenoid. Observe vacuum pump. If EVAP purge solenoid holds vacuum or is very slow to leak vacuum, service EVAP canister purge solenoid filter. If filter cannot be cleaned, replace EVAP canister purge solenoid. Go to step  20 . If EVAP purge solenoid does not hold vacuum or is not very slow to leak vacuum, remove vacuum pump. Reconnect all components. Go to next step.
    NOTE: Next step determines if any base engine concerns may have caused the misfire DTC or driveability problem.

  17. Check For Base Engine Concerns

    Perform engine compression test. Verify valve train is properly functioning. Check PCV system. Check for vacuum leaks. Repair as necessary. Go to step  20 . If no faults are identified, misfire DTC is intermittent. See INTERMITTENT  under SYSTEM TESTS.

  18. Check/Compare PID Values

    Turn all electrical accessories off. With KOEO, access DPFEGR PID. Record value. With KOER, access DPFEGR PID. Record value. Turn ignition off. Compare KOEO PID with KOER PID values. If KOEO value equals KOER value plus or minus 0.15 volts within the specification of 0.2-1.3 volts, disconnect scan tool. Go to next step. If KOEO value does not equal KOER value plus or minus 0.15 volts within the specification of 0.2-1.3 volts, go to step  20 .

  19. Check CMP Sensor Output

    Turn ignition off. Disconnect PCM connector. Install breakout box, leaving PCM connected to breakout box. Adjust DVOM to AC scale (to monitor less than 5 volts). Measure AC voltage between breakout box terminals No. 85 (CMP circuit) and 51 (PWR GND circuit). Record reading. Measure AC voltage between breakout box terminals No. 85 (CMP circuit) and 103 (PWR GND circuit). Record reading. If AC voltage varies more than 0.1 volt, verify CMP sensor is installed correctly. See CAMSHAFT POSITION SENSOR under ENGINE SENSORS & SWITCHES under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION article. If CMP sensor is correctly installed, replace faulty PCM. Go to next step. If AC voltage does not vary more than 0.1 volt, replace faulty CMP sensor. Go to next step.

  20. Drive Cycle

    Reconnect all electrical connectors. Using scan tool, clear DTC memory. Perform FUEL OR MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE  in MONITOR REPAIR VERIFICATION DRIVE CYCLES under DRIVE CYCLE PROCEDURES. Using scan tool, retrieve DTCs. If same DTC is not present, go to next step. If same DTC is present, replace faulty PCM. Go to next step.

  21. Verify Trouble Shooting Of DTCs Completed

    Perform QUICK TEST  under SELF-DIAGNOSTIC SYSTEM. If any DTC is present, go to applicable procedure for other DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no DTCs are set, trouble shooting is complete.
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