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Home >> Mazda >> 2003 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 26 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0301-P0304: Cylinders No. 1-4 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  12.
  2. Turn ignition switch off and then on. 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. Start engine and run at idle. Using scan tool, access PID data for ECT, IAT, MAF, RPM, TP and VS. Ensure all PID 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  12.
  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  12.
  5. Turn ignition switch off. Check suspect spark plug for cracks, gap, wetness and excessive wear. If spark plug is okay, go to next step. If plug is wet, flooding is suspected. Go to step  11. If spark plug is worn or damaged, replace as necessary and go to step  12.
  6. Check secondary ignition system. See BASIC DIAGNOSTIC PROCEDURES article. Repair or replace as necessary and go to step  12. If secondary ignition system is okay, go to next step.
  7. Check for vacuum leaks in intake-air system between dynamic chamber and intake manifold, and between intake manifold and cylinder head. Repair or replace as necessary and go to step  12. If no problem is found, go to next step.
  8. Remove intake-air system components as necessary to access and disconnect fuel injector harness connector at suspect cylinder. Connect Noid light to suspect injector harness connector. Check Noid light while cranking engine. If Noid light illuminates, go to next step. If Noid light does not illuminate, diagnose and repair fuel injector wire harness. After repair, go to step  12.
  9. 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 step  12.
  10. 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  12.
  11. Access and switch fuel injector in suspect cylinder with another fuel injector. Recheck while operating vehicle under conditions similar to when DTC was set. If DTC changes to cylinder where suspect fuel injector is installed, replace fuel injector and go to next step. If DTC does not change, go to next step.
  12. Reconnect all connectors. Start engine. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. 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 P0301-304 is present, replace PCM and go to next step. If DTC P0301-304 is not present, go to next step.
  13. 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.
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