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DTC Description
 
 
DTC DETECTION LOGIC
When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the crankshaft position (CKP) sensor signal to vary, ECM can determine that a misfire is occurring.
SensorInput signal to ECMECM function
Crankshaft position sensorEngine speedOn board diagnosis of misfire
The misfire detection logic consists of the following two conditions.
  1. One Trip Detection Logic (Three Way Catalyst Damage)
    On the 1st trip, when a misfire condition occurs that can damage the three way catalyst (TWC) due to overheating, the MIL will blink.
    When a misfire condition occurs, the ECM monitors the CKP sensor signal every 200 engine revolutions for a change.
    When the misfire condition decreases to a level that will not damage the TWC, the MIL will turn off.
    If another misfire condition occurs that can damage the TWC on a second trip, the MIL will blink.
    When the misfire condition decreases to a level that will not damage the TWC, the MIL will remain on.
    If another misfire condition occurs that can damage the TWC, the MIL will begin to blink again.
  2. Two Trip Detection Logic (Exhaust quality deterioration)
    For misfire conditions that will not damage the TWC (but will affect vehicle emissions), the MIL will only light when the misfire is detected on a second trip. During this condition, the ECM monitors the CKP sensor signal every 1,000 engine revolutions.
    A misfire malfunction can be detected on any one cylinder or on multiple cylinders.
DTCM.U.T.-III SE screen terms
(Trouble diagnosis content)
DTC detection condition
P030300CYL 3 MISFIRE
(Cylinder 3 misfire detected)
Diagnosis condition—
Signal (terminal)—
ThresholdNo. 3 cylinder misfires
Diagnosis delay time—
 
 
POSSIBLE CAUSE
  • Improper spark plug
  • Insufficient compression
  • Incorrect fuel pressure
  • The fuel injector circuit is open or shorted.
  • Fuel injector
  • Intake air leakage
  • The ignition signal circuit is open or shorted.
  • Lack of fuel
  • Signal plate
  • A/F sensor 1
  • Mass air flow sensor
  • Incorrect PCV hose connection
 
 
FAIL-SAFE
Engine operating condition in fail-safe mode
FAil safe modeVehicle behavior
Traveling control modeaccelerator angle variation controlECM controls the accelerator pedal depression speed to make it slower than actual speed. This causes a drop in accelerating performance and encourages the driver to repair malfunction.
noteECM does not control the accelerator releasing speed.
Combustion control modeIdle speed controlStops feedback control of idle speed and controls with specified speed.
Recovery speed control at deceleratingStops recovery speed control by the fuel cut at decelerating and controls with specified speed.
Idle neutral controlStops idle neutral control.
 
 
DTC Confirmation Procedure
1.PRECONDITIONING
If DTC Confirmation Procedure has been previously conducted, always perform the following procedure before conducting the next test.
  1. Turn ignition switch OFF and wait at least 10 seconds.
  2. Turn ignition switch ON.
  3. Turn ignition switch OFF and wait at least 10 seconds.
: .
 
2.PERFORM DTC CONFIRMATION PROCEDURE-1
  1. Start engine and warm it up to normal operating temperature.
  2. Turn ignition switch OFF and wait at least 10 seconds.
  3. Restart engine and let it idle for about 15 minutes.
  4. Check 1st trip DTC.
Is 1st trip DTC detected?
Proceed to DTC Diagnosis Procedure.
.
 
3.PERFORM DTC CONFIRMATION PROCEDURE-2
  1. Turn ignition switch OFF and wait at least 10 seconds.
  2. Start engine and drive the vehicle as per the similar conditions to (1st trip) Freeze Frame Data for a certain time. Refer to the table below.
    Hold the accelerator pedal as steady as possible.
    The similar conditions to (1st trip) Freeze Frame Data means the vehicle operation that the following conditions should be satisfied at the same time.
    cautionAlways drive vehicle in safe manner according to traffic conditions and obey all traffic laws when driving.
    Engine speedEngine speed in the freeze frame data ± 400 rpm
    Vehicle speedVehicle speed in the freeze frame data ± 10 km/h (6 MPH)
    Engine coolant temperature (T) conditionWhen the freeze frame data shows lower than 70°C (158°F),
    T should be lower than 70°C (158°F).
    When the freeze frame data shows higher than or equal to 70°C (158°F),
    T should be higher than or equal to 70°C (158°F).
    The time to driving varies according to the engine speed in the freeze frame data.
    Engine speedTime
    Around 1,000 rpmApproximately 10 minutes
    Around 2,000 rpmApproximately 5 minutes
    More than 3,000 rpmApproximately 3.5 minutes
  3. Check 1st trip DTC.
Is 1st trip DTC detected?
Proceed to DTC Diagnosis Procedure.
-1To check malfunction symptom before repair: Refer to Intermittent IncidentIntermittent Incident.
-2Confirmation after repair: INSPECTION END