LEMON Manuals: Even more car manuals for everyone
Home >> Mazda >> 2003 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 26 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0300: Random Misfire Detected >> Diagnosis & Repair Procedure

Diagnosis & Repair Procedure

WARNING: This page is about a different car, the 2002 Mazda Protege5 and 2002 Mazda Protege. However, it is still accessible from the selected car via links, so may be relevant.
  1. Turn ignition off. Connect scan tool to DLC-2. Turn ignition on, engine off. Monitor for FREEZE FRAME DATA and ensure data has been recorded. Check service bulletins for repair information related to this DTC. If repair information is not available, go to next step. If repair information is available, perform diagnosis and repair as necessary. After repair, go to step  21.
  2. Turn ignition switch off and then start engine. Using scan tool, check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If no other DTCs are present, go to next step. If DTCs are present, go to appropriate test.
  3. Using scan tool, access ECT, IAT, MAF, RPM, TP and VS PIDs. Start engine and run at idle. Ensure all signal data is within specification. See PIN VOLTAGE/PID VALUE CHARTS article. If all PID data is within specification, go to next step. If any PID data is not within specification, go to applicable test in SYSTEM & COMPONENT TESTING - MIATA, MILLENIA, MPV, PROTEGE, PROTEGE5 & 626 article and go to step  21.
  4. Referring to FREEZE FRAME DATA, operate vehicle under same conditions as when DTC was set. Record PID data for ECT, IAT, MAF, RPM, TP and VS. If all PID data is within specification, go to next step. If any PID data is not within specification, go to applicable test in SYSTEM & COMPONENT TESTING - MIATA, MILLENIA, MPV, PROTEGE, PROTEGE5 & 626 article. Diagnose and repair as necessary and go to step  21.
  5. Check CMP sensor operation. See BASIC DIAGNOSTIC PROCEDURES article. If CMP sensor is operating properly, go to next step. If CMP sensor is not operating properly, ensure CMP sensor is installed correctly, and timing belt and gears are not damaged before replacing CMP sensor and go to step  21.
  6. Check CKP sensor installation. See BASIC DIAGNOSTIC PROCEDURES article. Repair as necessary and go to step  21. If CKP sensor is not loose, go to next step.
  7. Start engine and allow to idle. Check ignition coil operation at each cylinder with timing light. If timing light flashes at all cylinders, go to step  10. If timing light does not flash as specified, go to next step.
  8. Disconnect ignition coil 3-pin harness connector. Turn ignition switch on. Measure voltage between ground and ignition coil 3-pin harness connector terminal "A" (Black/Blue wire). If battery voltage is present, go to next step. If battery voltage is not present, repair open in Black/Blue wire between ignition switch and ignition coil 3-pin harness connector terminal "A". See WIRING DIAGRAMS article. Go to step  21.
  9. Check ignition coil resistance. See BASIC DIAGNOSTIC PROCEDURES article. If ignition coil is okay, go to step  21. If ignition coil is faulty, replace ignition coil and go to step  21.
  10. Start engine. Using scan tool, access MAF PID data. Depress accelerator pedal to Wide Open Throttle (WOT) and release to race engine. MAF PID voltage reading should respond quickly with engine RPM. If MAF PID response is as specified, go to next step. If MAF PID response is not as specified, replace MAF sensor and go to step  21.
  11. Check for vacuum leaks in intake-air system between MAF sensor and throttle body. Also check for vacuum leaks at throttle body and dynamic chamber. Repair or replace as necessary and go to step  21. If no problem is found, go to next step.
  12. Check fuel line pressure. See FUEL PRESSURE (EXCEPT B2300, B3000, B4000 & TRIBUTE) under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. If fuel line pressure is okay, go to step  16. If fuel line pressure is to high, go to next step. If fuel pressure is to low, go to step  14.
  13. Disconnect vacuum hose from fuel pressure regulator. Start engine. If vacuum is present at hose, check fuel pump maximum pressure. See FUEL PRESSURE (EXCEPT B2300, B3000, B4000 & TRIBUTE) under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. Check fuel return hose for clogging or restriction. If no problems are found, replace fuel pressure regulator. After repair, go to step  21. If no vacuum is present at hose, check hose routing. If hoses are okay, replace Pressure Regulator Control (PRC) solenoid valve and go to step  21. If hoses are misrouted, repair as necessary and go to step  21.
  14. Check fuel pump maximum pressure. See FUEL PRESSURE (EXCEPT B2300, B3000, B4000 & TRIBUTE) under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. If maximum fuel pump pressure is 64-92 psi (4.5-6.5 kg/cm2 ), go to next step. If maximum fuel pump pressure is not as specified, repair open or poor connection in fuel pump circuit. If fuel pump circuit is okay, replace fuel pump and go to step  21.
  15. Check for leaks in fuel system from fuel pump to fuel rail. If any leaks are found, replace leaking fuel line and go to step  21. If no leaks are found, check for restriction at high pressure fuel filter and foreign material at low pressure fuel filter. If restriction is present at high pressure fuel filter, replace high pressure fuel filter. If foreign material is found in low pressure fuel filter, clean fuel tank and low pressure fuel filter. If fuel filters and fuel tank are okay, replace fuel pressure regulator and go to step  21.
  16. Check engine compression. See MECHANICAL INSPECTION under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES article. Engine compression should be a minimum of 119 psi (8.4 kg/cm2 ) at 300 RPM with a maximum variation of 28 psi (2 kg/cm2 ). If compression is as specified, go to next step. If compression is not as specified, repair as necessary and go to step  21.
  17. Turn ignition switch off. Disconnect both hoses from purge solenoid valve. Purge solenoid valve is located at rear of engine compartment. Blow air through purge solenoid valve. If air does not flow through valve, go to next step. If air flows through valve, replace purge solenoid valve and go to step  21.
  18. Check PCV valve operation. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - MIATA, MILLENIA, MPV, PROTEGE, PROTEGE5 & 626 article. Replace as necessary and go to next step. If PCV valve is okay, go to step  21.
  19. Remove EGR valve and ensure valve is not stuck open. If no problems are found, reinstall EGR valve and go to next step. If EGR valve is stuck open, replace or repair as necessary and go to step  21.
  20. Check cooling system for combustion gases. If no problem is found, go to next step. If combustion gases are found in cooling system, repair leak and go to next step.
  21. Reconnect all connectors. Turn ignition switch on. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Start engine. Using scan tool, perform DRIVE MODE 1 - PCM ADAPTIVE MEMORY  under SELF-DIAGNOSTIC SYSTEM. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If DTC P0300 is present, replace PCM and go to next step. If DTC P0300 is not present, go to next step.
  22. Cycle ignition switch from off to on. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If no other DTCs are present, testing is complete. If any other DTC is present, go to applicable test and repair.
scientia non olet · About LEMON Manuals