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Home >> Mazda >> 2002 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 60 (Engine Controls [Self-Diagnostics 2.3L]) >> Diagnostic Tests >> DTCS P0301, P0302, P0303 & P0304 >> 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, 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 PID values are okay with engine running, go to next step. If any signal is far out of specification when engine is running, check suspect sensor for fault or suspect circuit for excessive resistance. Repair or replace as necessary. After repair, go to step  12.
  5. Verify Current Input Signal Status Under Trouble Condition -  Inspect same PIDs as in step  4 while simulating FREEZE FRAME DATA condition. If any signal causes drastic changes, check suspect sensor for fault or suspect circuit for excessive resistance. Repair or replace as necessary. After repair, go to step  12.
  6. Inspect Spark Plug Condition -  Turn ignition off. Remove spark plug from suspected cylinder. Inspect spark plug condition:
    • Cracks
    • Excess wear
    • Gap
    • Wet
    If any problem is found on spark plug:
    • If spark plug is wet, fuel flooding is suspected. After repair, go to step  12.
    • If spark plug has a cracks, excessive wear or improper gap, replace faulty spark plug. After repair, go to step  12.
  7. Verify High-Tension Lead Condition -  Remove high-tension lead. Inspect high-tension lead:
    • Condition and resistance
    • Cracks
    • Spark shorts to cylinder head through high-tension lead insulator
    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.
  8. Inspect For Air Suction At Intake-Air System -  Inspect for air leakage at following:
    • Around connection of dynamic chamber and intake manifold
    • Around connection of intake manifold and cylinder head
    If air leakage is not found, go to next step. If air leakage is found, repair or replace suspected part. After repair, go to step  12.
  9. Inspect Fuel Injector Harness -  Remove intake air system parts. Disconnect fuel injector 2-pin harness connector on suspected cylinder. Connect noid light to fuel injector 2-pin harness connector terminals. Check for dim light during cranking. If noid light is illuminated, go to next step. If noid light illuminates dimly, inspect fuel injector harnesses. Repair or replace wire harness as necessary. After repair, go to step  12.
    10. 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 to 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.
  10. 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 step  12. If small bubbles are not present, go to next step.
  11. 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 next step.
  12. Inspect Fuel Injector Operation -  Remove fuel injector from suspected cylinder. Swap suspected fuel injector with fuel injector on another cylinder. Start engine and run at idle. If misfire DTC is not for cylinder with suspected fuel injector, go to next step. If misfire DTC is for cylinder which has a suspected fuel injector, replace suspected fuel injector. After repair, go to next step.
  13. Verify Trouble Shooting Of Misfire DTC Is Completed -  Make sure to reconnect all disconnected connectors. Clear DTC from PCM memory using WDS or equivalent. Turn ignition off. Start engine. Perform MODE 1 - PCM ADAPTIVE MEMORY PRODUCE DRIVE MODE  under DRIVE CYCLES. If PENDING CODE of same DTC is not present, go to next step. If PENDING CODE of 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.
  14. 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.
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