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Home >> Mazda >> 2007 >> B4000 SE, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 70 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0300, DTC P0301, DTC P0302, DTC P0303, DTC P0304, DTC P0305, DTC P0306 Or DTC P0316 >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Mazda B4000, 2003 Mazda B3000, and 2003 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  14 .
    • For all others, go to next step.
  2. 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  testing under SYSTEM TESTS.
    FUEL PRESSURE SPECIFICATIONS

    Engine psi (kPa)
    2.3L 35-55 (240-380)
    3.0L & 4.0L 30-65 (207-448)
  3. 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  7 .
  4. Check Resistance Of Fuel Injector(s) & Harness -  Turn ignition off. Disconnect PCM 104-pin harness connector. Connect Breakout Box (49-UN01-130) to PCM harness connector only. See Figure . Measure resistance of suspect INJ circuit between breakout box terminals No. 71 or 97 (VPWR circuit) and suspect fuel injector breakout box terminal. See INJ CIRCUIT IDENTIFICATION  . See Fig 1 . If resistance reading is 11-13 ohms (2.3L), 8.5-15.5 ohms (3.0L) or 11-18 ohms (4.0L), replace faulty PCM. After repair, go to step  17 . If resistance reading is not as specified, go to next step.
    INJ CIRCUIT IDENTIFICATION

    Injector Breakout Box Terminal Wire Color
    1 No. 75 Tan
    2 No. 101 White
    3 No. 74 Brown/Yellow
    4 No. 100 Brown/Light Blue
    5 No. 73 Tan/Black
    6 No. 99 Light Green/Orange
    Fig 1: Fuel Injector Harness Connector & Circuit Identification
    G00155536Courtesy of MAZDA MOTORS CORP.
  5. Check Resistance Of Fuel Injector Harness -  Disconnect suspect fuel injector 2-pin 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 appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. After repair, go to step  17 .
  6. 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 not as specified, repair short circuit. After repair, go to step  17 .
  7. 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. After repair, go to step  17 . If misfire did not move to cylinder with suspect fuel injector, go to next step.
  8. 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. After repair, go to step  17 .
  9. 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  17 .
    10. NOTE: Misfire Monitor can be influenced by Evaporative Emission (EVAP) system. Next five test steps will diagnose EVAP system.
  10. Check Evaporative Emission System -  Inspect EVAP canister for fuel saturation. If an excess amount of liquid fuel is present, replace EVAP canister. After repair, go to step  17 . If an excess amount of liquid fuel is not present, check fuel tank vent system. Go to next step.
  11. Pressure Test Evaporative 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. After repair, go to step  17 .
  12. Check Vacuum In Evaporative 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. After repair, go to step  17 . If a fault is not located, go to next step.
  13. Check For Evaporative 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 port. 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. After repair, go to step  17 .
  14. 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 port. 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 purge solenoid filter. If filter cannot be cleaned, replace EVAP purge solenoid. After repair, go to step  17 . 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.
    15. NOTE: Next step determines if any base engine concerns may have caused the misfire DTC or driveability problem.
  15. 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. After repair, go to step  17 . If no faults are identified, misfire DTC is intermittent. See INTERMITTENT  testing under SYSTEM TESTS.
  16. 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 in REMOVAL, OVERHAUL & INSTALLATION article. If CMP sensor is correctly installed, replace faulty PCM. After repair, go to next step. If AC voltage does not vary more than 0.1 volt, replace faulty CMP sensor. After repair, go to next step.
  17. Drive Cycle -  Reconnect all electrical connectors. Using scan tool, clear DTC from 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. After repair, go to next step.
  18. 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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