LEMON Manuals: Even more car manuals for everyone
Home >> Mazda >> 2002 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 61 (Engine Controls [Self-Diagnostics 3.0L]) >> Diagnostic Tests >> DTC P0300: Random Misfire Detected >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.
  1. If FREEZE FRAME DATA has been recorded, go to next step. If FREEZE FRAME DATA has not been recorded, record FREEZE FRAME DATA. Go to next step.
  2. Verify Related Repair Information Availability -  Check for related Service Bulletins and/or on-line repair information availability. If any related repair information is available, perform repair or diagnosis according to available repair information. If vehicle is not repaired, go to next step. If related repair information is not available, go to next step.
  3. Verify Related Pending Code Or Stored DTCs -  Turn ignition off, then on (engine off). Verify related PENDING CODE or stored DTCs. If no other DTCs are present and a driveability concern is not present, go to next step. If no other DTCs are present, go to next step. If any other DTC is present, go to appropriate DTC trouble shooting procedure. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  4. Verify Current Input Signal Status (Ignition Key To On/Idle) -  Access APP1, APP2, ECT, IAT, MAF, RPM, TP_REL, and VSS PIDs using WDS or equivalent. Refer to PIN VOLTAGE & PID VALUE CHART INDEX in PIN VOLTAGE CHARTS article. If all signals are within specification when ignition is on and engine is running at idle, go to next step. If any signal is far out of specification when ignition is on and engine is running at idle, check suspected circuit and/or part according to inspection results. After repair, go to step  19.
  5. Verify Current Input Signal Status Under Trouble Condition -  Check same PIDs as in step  4 while simulating FREEZE FRAME DATA condition. If no signal is present which cause drastic changes, go to next step. If any signal is present which causes drastic changes, check suspected circuit and/or part according to inspection results. After repair, go to step  19.
  6. Inspect CMP Sensor -  Inspect CMP sensors. See CAMSHAFT POSITION SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - MAZDA6, MIATA, MPV, PROTEGE & PROTEGE5 article. If CMP sensors are okay, go to next step. If CMP sensors are faulty, check installation condition and damage on timing chains and gears, repair faulty components. If okay, replace faulty CMP sensor(s). Refer to CAMSHAFT POSITION SENSOR in REMOVAL & INSTALLATION article. After repair, go to step  19.
  7. Verify CKP Sensor Installation Condition -  Inspect for CKP sensor looseness. If CKP sensor is tight, go to next step. If CKP sensor is loose, retighten CKP sensor. Refer to CRANKSHAFT POSITION SENSOR in REMOVAL & INSTALLATION article. After repair, go to step  19.
  8. Inspect Ignition System Operation -  Perform Spark Test. SPARK TEST  under SYSTEM TESTS. If result of Spark Test is okay, go to next step. If result of Spark Test is no okay, repair or replace malfunctioning part according to Spark Test results. After repair, go to step  19.
  9. Inspect MAF PID -  Start engine. Access MAF PID using WDS or equivalent. Verify MAF PID changes quickly according to racing of engine RPM. If MAF PID response is okay, go to next step. If MAF PID response is not okay, replace MAF/IAT sensor. After repair, go to step  19.
  10. Inspect Excessive Air Suction In Intake Air System -  Check for air leakage at following:
    • Between MAF/IAT sensor and throttle body
    • Between throttle body and dynamic chamber
    If air leakage is not present, go to next step. If any air leakage is present, repair or replace suspected part. After repair, go to step  19.
  11. Inspect Fuel Line Pressure -  Inspect fuel line pressure. Refer to FUEL PRESSURE (EXCEPT B2300, B3000, B4000 & TRIBUTE) under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. If fuel line pressure is too low, go to next step. If fuel line pressure is okay, go to step  18. If fuel line pressure is too high, replace fuel pressure regulator. Refer to FUEL PRESSURE REGULATOR under FUEL SYSTEM in REMOVAL & INSTALLATION article. After repair, go to step  19.
  12. Inspect Fuel Line From Fuel Pump To Fuel Delivery Pipe -  Visually check fuel line for any leakage. If any fuel leakage is present, replace suspected fuel line. After repair, go to step  19. If fuel leakage is not present, check low-pressure side fuel filter for foreign materials or stain inside fuel filter. If foreign material or stain is found inside low-pressure side fuel filter, clean out fuel tank and low-pressure side filter. If foreign material or stain is not found in low-pressure side fuel filter, replace fuel pump unit. After repair, go to step  19.
  13. Inspect Engine Compression -  Inspect engine compression. Refer to MECHANICAL INSPECTION in BASIC DIAGNOSTIC PROCEDURES article. If engine compression is okay, go to next step. If engine compression is not okay, perform engine overhaul for repairs. After repair, go to step  19.
  14. Inspect Variable Valve Timing Control System Operation -  Inspect variable valve timing control system operation. Refer to VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION INSPECTION  under SYSTEM TESTS. If variable valve timing control system is working properly, go to next step. If variable valve timing control system is not working properly, repair or replace malfunctioning part according to variable valve timing control system inspection results. After repair, go to step  19.
  15. Inspect Operation Of Purge Control Solenoid Valve -  Inspect purge control system operation. Refer to PURGE CONTROL SYSTEM INSPECTION  under SYSTEM TESTS. If purge control system is working properly, go to next step. If purge control system is not working properly, repair or replace malfunctioning part according to purge control system inspection results. After repair, go to step  19
  16. Inspect PCV Valve Operation -  Turn ignition off. Remove PCV valve and inspect valve operation. Refer to POSITIVE CRANKCASE VENTILATION under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - MAZDA6, MIATA, MPV, PROTEGE & PROTEGE5 article. If PCV valve is operating properly, go to next step. If PCV valve is faulty, replace PCV valve. After repair, go to step  19.
  17. Inspect Operation Of EGR Valve -  Remove EGR valve. Visually inspect valve for sticking open. Refer to EXHAUST GAS RECIRCULATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - MAZDA6, MIATA, MPV, PROTEGE & PROTEGE5 article. If EGR valve is okay, go to next step. If EGR valve is stuck open, replace EGR valve. After repair, go to step  19.
    18. WARNING: Removing radiator cap when radiator is hot is dangerous. Scalding coolant and steam may shoot out and cause serious injury. When removing radiator cap, wrap a thick cloth around cap and turn it slowly.
    NOTE: If there are any small bubbles which make engine coolant White at filler opening, air is getting in from poor sealing at head gasket or other areas between combustion chamber and engine coolant passage. Large bubbles are normal since they are remaining air coming out from engine coolant passage.
  18. Inspect Sealing Of Engine Coolant Passage -  Remove radiator cap. Perform procedure to bleed air from engine coolant, then run engine at idle. If there are any small bubbles which make engine coolant White at filler opening, repair or replace faulty parts. After repair, go to next step. If small bubbles are not present, go to next step.
  19. Verify Trouble Shooting Of DTC P0300 Is Completed -  Make sure to reconnect all disconnected connectors. Turn ignition on, engine off. Clear DTC from PCM memory using WDS or equivalent. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Start engine. Perform MODE 1 - PCM ADAPTIVE MEMORY PRODUCE DRIVE MODE . If PENDING CODE for same DTC is not present, go to next step. If PENDING CODE for same DTC is present, replace PCM. For PCM removal and installation, see POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION article. After repair, go to next step.
  20. Verify After Repair Procedure -  Using scan tool, perform After Repair Procedure. See AFTER REPAIR PROCEDURE . If any DTCs are present, go to appropriate DTC inspection. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are present, trouble shooting is complete.
scientia non olet · About LEMON Manuals