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.
Test Procedure
- JB1 VISUAL INSPECTION OF THE IGNITION SYSTEM
- Visually inspect the engine compartment to make sure all the coils are properly and securely connected.
- Examine all the wiring harnesses and connectors for damaged, burned, or overheated insulation, and loose or broken conditions.
- Make sure the vehicle battery is in good condition and all accessories are turned off.
Is a concern indicated?
Yes No REPAIR as necessary.
Clear the PCM DTCs. REPEAT the self-test.GO to JB2. - JB2 DIAGNOSTIC TROUBLE CODE (DTC) P0301 THROUGH P0304: MISFIRE ON CYLINDERS 1 THROUGH 4
Are any of the above listed DTCs present?
Yes No GO to JB3. GO to JB4. - JB3 CHECK FOR SPARK AT CYLINDER(S) INDICATED BY THE DTC(S)
- Ignition OFF.
- Disconnect the ignition coil(s) from the spark plug(s).
- Connect air gap spark tester 303-D037 (D81P-6666-A) or equivalent to a coil.
- Crank the engine using the engine cranking diagnostic mode. Refer to DIAGNOSTIC MODES .
- Observe the spark tester while cranking the engine.
Is a bluish-white spark present?
Yes No GO to JB5. INSPECT the coil boot on the missing cylinder. INSTALL a new coil as necessary. INSPECT the spark plug on the missing cylinder. MEASURE the resistance of the spark plug. INSTALL a new spark plug if the resistance is lower than 2,000 ohms or higher than 20,000 ohms.
GO to PINPOINT TEST JF . - JB4 CHECK FOR SPARK AT ALL CYLINDERS
- Ignition OFF.
- Disconnect the ignition coil(s) from the spark plug(s).
- Connect the air gap spark tester 303-D037 (D81P-6666-A) or its equivalent to the suspect coil.
- Crank the engine using the engine cranking diagnostic mode. Refer to DIAGNOSTIC MODES .
- Observe the spark tester at each cylinder while cranking the engine.
Is a bluish-white spark consistent between all cylinders?
Yes No GO to JB5. INSPECT the coil boot on the missing cylinder. INSTALL a new coil as necessary. INSPECT the spark plug on the missing cylinder. MEASURE the resistance of the spark plug. INSTALL a new spark plug if the resistance is lower than 2,000 ohms or higher than 20,000 ohms.
RECORD cylinder(s) with inconsistent spark.
GO to PINPOINT TEST JF . - JB5 CHECK THE SPARK PLUGS
- Ignition OFF.
- Remove and inspect the plugs for damage, wear, carbon deposits, and proper plug gap.
Are the plugs OK?
Yes No GO to JB6. ADJUST the gap or INSTALL a new spark plug as necessary. - JB6 CHECK THE SPARK PLUG RESISTANCE
- Measure the spark plug resistance.
Is the resistance between 2,000 and 20,000 ohms?
Yes No GO to JB7. INSTALL a new spark plug. - JB7 TEST DIRECTION
Were you directed to this pinpoint test from ENGINE CONTROLS - SYMPTOM CHARTS -- FUSION HYBRID, MILAN HYBRID & MKZ HYBRID ?
Yes No RETURN to SYMPTOM CHARTS for further direction. GO to JB8. - JB8 TEST DIRECTION
Were you directed to this pinpoint test from Pinpoint Test Step A6?
Yes No GO to A8. The concern is intermittent.
GO to JB9. - JB9 TEST DIRECTION
Were you directed to this pinpoint test from Pinpoint Test Step HD6?
Yes No GO to HD7. The concern is intermittent.
GO to PINPOINT TEST Z .
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.