Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSKIA2015OPTIMA SX TURBOREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 107 (ENGINE CONTROL SYSTEM DIAGNOSIS (2 OF 3) - 2.4L (EXCEPT HEV))DTC P0303: CYLINDER 3 - MISFIRE DETECTEDSYSTEM INSPECTIONIGNITION SYSTEM INSPECTION

2015 Kia Optima SX Turbo

Ignition System Inspection

2015 Kia Optima SX TurboSECTION Ignition System Inspection

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

Misfire Inspection
1. Check the cylinder where the misfire occurs after replacing the ignition coil of the cylinder where the misfire has occurred with the ignition coil of the other cylinder.
2. Does the misfiring cylinder change?
  YES
  - Go to "IGNITION COIL WAVEFORM INSPECTION" procedure below.
  NO
3. Repair as necessary except for the ignition coils and go to "FUEL SYSTEM INSPECTION" procedure below.
Ignition coil waveform inspection
1. Ignition "ON" and engine "ON".
2. Measure the voltage between control terminal of ignition soil harness connector and chassis ground.
  Specification: Refer to Fig.1
  
  Fig 1: Measuring Voltage Between Control Terminal Of Ignition Coil Harness Connector And Chassis Ground
  Courtesy of KIA MOTOR AMERICA, INC.
Spark Plug & Ignition Coil Inspection
1. Visually/Physically inspect the spark plug and ignition coil related to the misfiring cylinder(s) for the following conditions.
  - Damage, cracks, carbon and flashover
  - Poor connection or damaged harness
  - Connected to the incorrect cylinders at the ignition coil and spark plug
2. Measure the resistance of the primary and secondary ignition coil related to the misfiring cylinder(s).
  Specification:
  
  Primary Ignition Coil Resistance : 0.56 ~ 0.68? at 20°C (68°F)
  
  Secondary Ignition Coil Resistance : 6 ~ 8k? at 20°C (68°F)
  
  Fig 2: Testing Primary & Secondary Ignition Coil Resistance
  Courtesy of KIA MOTORS AMERICA, INC.
3. Was a problem found in any of the above areas?
  YES
  - Repair or replace as necessary and go to "VERIFICATION OF VEHICLE REPAIR " procedure.
  NO
  - Go to next step as below.
Spark Plug Inspection
1. Visually/Physically inspect the spark plug related to the misfiring cylinder(s) for the following conditions.
  - Damaged insulation, Worn electrodes, Oil or fuel fouled, Loose terminals and cracks
  - Check for electrode gap : 1.0 - 1.1 mm (0.039 - 0.043 in.)
  - Check if the spark plug for the relevant cylinder is lighter in color than the other plugs.
2. Was a problem found in any of the above areas?
  YES
  - Repair or replace as necessary and go to "VERIFICATION OF VEHICLE REPAIR " procedure.
  NO
  - Go to next step as below.

RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.