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2008 - MX-5 - Engine

DTC P0301, P0302, P0303, P0304 [LF]



DTC P0301

DTC P0302

DTC P0303

DTC P0304

Cylinder No.1 misfire detected

Cylinder No.2 misfire detected

Cylinder No.3 misfire detected

Cylinder No.4 misfire detected

DETECTION CONDITION

  • The PCM monitors CKP sensor input signal interval time. The PCM calculates the change of interval time for each cylinder. If the change of interval time exceeds the preprogrammed criteria, the PCM detects a misfire in the corresponding cylinder. While the engine is running, the PCM counts number of misfires that occurred at 200 crankshaft revolutions and 1,000 crankshaft revolutions and calculates misfire ratio for each crankshaft revolution. If the ratio exceeds the preprogrammed criteria, the PCM determines that a misfire, which can damage catalytic converter or affect emission performance, has occurred.

    Diagnostic support note
  • This is a continuous monitor (Misfire).

  • The MIL illuminates if the PCM detects the misfire which affects emission performance in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.

  • The MIL flashes if the PCM detects the misfire which can damage the catalytic converter during the first drive cycle.

  • PENDING CODE is available if the PCM detects the misfire which affects emission performance during the first drive cycle.

  • FREEZE FRAME DATA is available.

  • The DTC is stored in the PCM memory.

POSSIBLE CAUSE

  • Spark plug malfunction

  • Ignition system malfunction

  • Fuel injector malfunction

  • Air suction in intake air system (between dynamic chamber and cylinder head)

  • Inadequate engine compression due to engine internal malfunction

  • Related connector or terminal malfunction

  • Related wiring harness malfunction


Diagnostic procedure

STEP

INSPECTION

ACTION

1

VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED
  • Have FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS (Misfire related) been recorded?

Yes

Go to the next step.

No

Record the FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on the repair order, then go to the next step.

2

VERIFY RELATED REPAIR INFORMATION AVAILABILITY
  • Verify related Service Bulletins and/or on-line repair information availability.

  • Is any related repair information available?

Yes

Perform repair or diagnosis according to the available repair information.

  • If the vehicle is not repaired, go to the next step.

No

Go to the next step.

3

VERIFY RELATED PENDING CODE OR STORED DTC
  • Turn the ignition switch off then to the ON position (Engine off).

  • Verify related pending code or stored DTCs.

  • Is other DTCs present?

Yes

Go to the appropriate DTC troubleshooting.

(See DTC TABLE [LF].)

No

Go to the next step.

4

VERIFY CURRENT INPUT SIGNAL STATUS (KEY TO ON /IDLE)
  • Access APP1, APP2, ECT, IAT, MAF, RPM, TP and VSS PIDs using M-MDS.

    (See PCM INSPECTION [LF].)

  • Is there any signal that is far out of specification when ignition switch is turned to the ON position and engine idles?

Yes

Inspect suspected circuit and/or part according to inspection results. Then go to Step 14.

(See PCM INSPECTION [LF].)

No

Go to the next step.

5

VERIFY CURRENT INPUT SIGNAL STATUS UNDER TROUBLE CONDITION
  • Inspect same PIDs as in Step 4 while simulating FREEZE FRAME DATA condition.

  • Is there any signal which causes drastic changes?

Yes

Inspect suspected circuit and/or part according to inspection results. Then go to Step 14.

(See PCM INSPECTION [LF].)

No

Go to the next step.

6

INSPECT SPARK PLUG CONDITION
  • Turn the ignition switch off.

  • Remove spark plug from suspected cylinder.

  • Inspect spark plug condition:

    • Cracks

    • Excess wear

    • Gap

    • Wet

  • Is any problem found on spark plug?

Yes

  • If spark plug is wet, fuel flooding is suspected. Then go to Step 14.

  • If spark plug has a cracks, excessive wear or improper gap, replace the malfunctioning spark plug. Then go to Step 14.

    (See FUEL INJECTOR REMOVAL/INSTALLATION [LF].)

No

Go to the next step.

7

INSPECT IGNITION COIL HARNESSES
  • Inspect the ignition coil related harness condition (intermittent open or short) for suspected cylinder.

  • Are harness conditions normal?

Yes

Go to the next step.

No

Repair suspected wiring harnesses, then go to Step 14.

8

INSPECT IGNITION SYSTEM OPERATION

Yes

Go to the next step.

No

Repair or replace malfunctioning part according to spark test result.

Then go to Step 14.

9

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

  • Is air leakage found?

Yes

Repair or replace suspected part, then go to Step 14.

No

Go to the next step.

10

INSPECT FUEL INJECTOR WIRING HARNESS
  • Remove intake air system parts.

  • Disconnect the fuel injector connector on suspected cylinder.

  • Connect NOID LIGHT to fuel injector terminals.

  • Inspect dim of light during cranking.

  • Does the light illuminate?

Yes

Go to the next step.

No

Inspect for fuel injector wiring harnesses.

Repair or replace it if necessary, then go to Step 14.

11

INSPECT SEALING OF ENGINE COOLANT PASSAGE

Yes

Repair or replace malfunctioning part according to inspection results.

Then go to Step 14.

No

Go to the next step.

12

INSPECT ENGINE COMPRESSION

Yes

Go to the next step.

No

Overhaul the engine, then go to the next step.

13

INSPECT FUEL INJECTOR OPERATION
  • Remove the fuel injector from suspected cylinder.

  • Switch the injector with the injector on other cylinder.

  • Start the engine and idle it.

  • Is misfire DTC for cylinder which has a suspected fuel injector?

Yes

Replace the injector, then go to the next step.

(See FUEL INJECTOR REMOVAL/INSTALLATION [LF].)

No

Go to the next step.

14

VERIFY TROUBLESHOOTING OF MISFIRE DTC COMPLETED
  • Make sure to reconnect all disconnected connectors.

  • Start the engine.

  • Clear the DTC from the PCM memory using the M-MDS.

  • Perform the KOER self-test (using M-MDS) or the HO2S heater, HO2S, and TWC Repair Verification Drive Mode (not using M-MDS).

    (See KOEO/KOER SELF TEST [LF].)

    (See OBD-II DRIVE MODE [LF].)

  • Is the PENDING CODE for this DTC present?

Yes

Replace the PCM, then go to the next step.

(See PCM REMOVAL/INSTALLATION [LF].)

No

Go to the next step.

15

VERIFY AFTER REPAIR PROCEDURE

Yes

Go to the applicable DTC troubleshooting.

(See DTC TABLE [LF].)

No

Troubleshooting completed.




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