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Home >> Mazda >> 2021 >> CX-5 Sport, FWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 22 (On-Board Diagnostic - Engine Control (VIN Y) (1 Of 3)) >> DTC P0300-00: Random Misfire Detected >> Troubleshooting Diagnostic Procedure >> Intention of troubleshooting procedure

Intention of troubleshooting procedure

WARNING: This page is about a different variant/trim than selected.
TROUBLESHOOTING DIAGNOSTIC PROCEDURE

STEP INSPECTION RESULTS ACTION
1 PURPOSE: DETERMINE INTEGRITY OF SPARK PLUG
Yes Replace the spark plug, then go to Step 10.
(See SPARK PLUG REMOVAL/INSTALLATION [VIN Y] .)
No Go to the next step.
2 PURPOSE: DETERMINE INTEGRITY OF IGNITION COIL
Yes Replace the ignition coil/ion sensor, then go to Step 10.
(See IGNITION COIL/ION SENSOR REMOVAL/INSTALLATION [VIN Y] .)
No Go to the next step.
3 PURPOSE: DETERMINE INTEGRITY OF FUEL INJECTOR
Yes Replace the fuel injector, then go to Step 10.
(See FUEL INJECTOR REMOVAL/INSTALLATION [VIN Y] .)
No Go to the next step.
4 PURPOSE: VERIFY IF MALFUNCTION RELATED TO INTAKE-AIR SYSTEM IS CAUSE OF MISFIRE
  • Visually inspect for loose, cracked or damaged hoses on intake air system.
  • Is there any malfunction?
Yes Repair or replace the malfunctioning part according to the inspection results, then go to Step 10.
No Go to the next step.
5 PURPOSE: VERIFY IF POOR DRIVE BELT ASSEMBLY IS CAUSE OF MISFIRE
Yes Assemble drive belt correctly, then go to Step 10.
(See DRIVE BELT REMOVAL/INSTALLATION [VIN Y] .)
No Go to the next step.
6 PURPOSE: VERIFY IF FOREIGN MATTER ON DRIVE BELT IS CAUSE OF MISFIRE
  • Verify if oil is on the drive belt.
  • Is there foreign matter on the drive belt?
Yes Remove the foreign matter on the drive belt, then go to Step 10.
No Go to the next step.
7 PURPOSE: DETERMINE INTEGRITY OF DRIVE BELT AUTO TENSIONER
Yes Replace the drive belt auto tensioner, then go to Step 10.
(See DRIVE BELT AUTO TENSIONER REMOVAL/INSTALLATION [VIN Y] .)
No Go to the next step.
8 PURPOSE: VERIFY IF MALFUNCTION RELATED TO ENGINE COMPRESSION IS CAUSE OF MISFIRE
Yes Go to the next step.
No Replace or overhaul the engine, then go to Step 10.
9 PURPOSE: VERIFY IF MALFUNCTION RELATED TO SEALING OF ENGINE UNIT (COMBUSTION CHAMBER AND ENGINE COOLANT PASSAGE) IS CAUSE OF MISFIRE
  • Perform the "ENGINE COOLANT LEAKAGE INSPECTION". (See ENGINE COOLANT LEAKAGE INSPECTION [VIN Y] .)
  • Does the radiator cap tester needle drop even though there is no engine coolant leakage from the radiator or the hoses?
Yes Engine coolant leakage from the engine (between the combustion chamber and the engine coolant passage) may have occurred.
  • Verify the conditions of the gasket and the cylinder head.
    • If there is any malfunction:
      • Repair or replace the malfunctioning part according to the inspection results, then go to the next step.
No Go to the next step.
10 PURPOSE: VERIFICATION OF VEHICLE REPAIR COMPLETION
Yes Repeat the inspection from Step 1.

Go to the next step.
No Go to the next step.
11 PURPOSE: VERIFY IF THERE IS ANY OTHER MALFUNCTION
  • Is any other DTC or pending code stored?
Yes Go to the applicable DTC inspection.
(See DTC TABLE .)
No DTC troubleshooting completed.