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Home >> Mazda >> 2003 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 61 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0301, DTC P0302, DTC P0303 Or DTC P0304 >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Mazda Protege5 and 2003 Mazda Protege. However, it is still accessible from the selected car via links, so may be relevant.
  1. Verify Related Repair Information Availability -  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. Verify Related Pending Code & Stored DTCs -  Turn ignition off, then start engine. Using scan tool, check for pending code related DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If no other DTCs are present, go to next step. If any other DTCs are present, go to appropriate trouble shooting procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  3. Verify Current Input Signal Status (Ignition Key To On /Idle) -  Start engine and run at idle. Using scan tool, access ECT, IAT, MAF, RPM, TP and VS PIDs. Ensure all PID data is within specification. See PIN VOLTAGE CHARTS article. If all PID data is within specification, go to next step. If any PID data is far out of specification, go to applicable test procedure in SYSTEM & COMPONENT TESTING - MAZDA6, MIATA, MPV, PROTEGE & PROTEGE5 article. After repair, go to step  12.
  4. Verify Current Input Signal Status Under Trouble Condition -  Monitor ECT, IAT, MAF, RPM, TP and VS PIDs while simulating FREEZE FRAME DATA condition. If no drastic changes occur to any signals, go to next step. If any signal is drastically changed, go to applicable test in SYSTEM & COMPONENT TESTING - MAZDA6, MIATA, MPV, PROTEGE & PROTEGE5 article. Diagnose and repair as necessary. After repair, go to step  12.
  5. Inspect Spark Plug Condition -  Turn ignition off. Remove spark plug from suspect cylinder and check for cracks, gap, wetness and excessive wear. If spark plug is okay, go to next step. If plug is wet and fuel flooding is suspected, go to step  11. If spark plug has cracks, excessive wear or improper gap, replace spark plug. After repair, go to step  12.
  6. Verify High-Tension Lead Condition -  Check high-tension lead condition and resistance (cracks or spark shorts to cylinder head through high-tension lead insulator). See BASIC DIAGNOSTIC PROCEDURES article. If high tension lead is okay, go to next step. If high-tension lead is faulty, replace high tension lead. After repair, go to step  12.
  7. Inspect For Air Suction At Intake-Air System -  Check for air leaks in intake-air system between dynamic chamber and intake manifold, and between intake manifold and cylinder head. If no air leak is detected, go to next step. If any air leak is detected, repair or replace suspect part as necessary. After repair, go to step  12.
  8. Inspect Fuel Injector Harness -  Remove intake-air system components as necessary to access and disconnect fuel injector 2-pin harness connector at suspect cylinder. Connect Noid light to suspect injector harness connector. Check dimming of Noid light while cranking engine. If Noid light dims during cranking, go to next step. If Noid light does not dim as specified, diagnose and repair fuel injector wire harness. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. After repair, go to step  12.
  9. Inspect Sealing Of Engine Coolant Passage -  Check cooling system for combustion gasses. Remove radiator cap. Bleed air from cooling system. Start engine and let idle. Check for small bubbles which make coolant white at filler neck. If combustion gasses are not present, go to next step. If combustion gasses are present, repair leak as necessary. After repair, go to step  12.
  10. Inspect Engine Compression -  Check engine compression. See MECHANICAL INSPECTION under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES article. If compression is okay, go to next step. If compression is not okay, repair as necessary. After repair, go to step  12.
  11. Inspect Fuel Injector Operation -  Remove fuel injector from suspect cylinder and switch with another fuel injector. Start engine and run at idle. If DTC changes to cylinder where suspect fuel injector is installed, replace fuel injector. After repair, go to next step. If DTC does not change, go to next step.
  12. Verify Trouble Shooting Of Misfire DTC Completed -  Reconnect all connectors. Turn ignition on, engine off. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Start engine. Using scan tool, perform MODE 1 - PCM ADAPTIVE MEMORY PROCEDURE DRIVE MODE  under SELF-DIAGNOSTIC SYSTEM. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If DTC P0301-P0304 is present, replace PCM. For PCM removal and installation, see POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION article. After repair, go to next step. If same DTC P0301-P0304 is not present, go to next step.
  13. Verify After Repair Procedure -  Using scan tool, perform After Repair Procedure. See AFTER REPAIR PROCEDURE . If no other DTCs are present, testing is complete. If any other DTC is present, follow appropriate DTC diagnostic procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
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