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 MANUALSMERCURY2003SABLE GS, 4D WAGON, 3.0 2, AX4SREPAIR AND DIAGNOSISENGINE PERFORMANCETHEORY AND OPERATIONENGINE CONTROLS - THEORY & OPERATION - CNG, FLEX-FUEL & GASOLINECOMPUTERIZED ENGINE CONTROLSOUTPUT DEVICESCOIL ON PLUG

2003 Mercury Sable GS, 4D Wagon, 3.0 2, AX4S

Coil On Plug

2003 Mercury Sable GS, 4D Wagon, 3.0 2, AX4SSECTION Coil On Plug

Coil On Plug (COP) ignition operates similar to a standard coil pack ignition except each spark plug has one coil per spark plug. See Fig 1. COP has 3 different modes of operation:

Engine Cranking

During engine cranking, PCM will fire 2 spark plugs simultaneously. One spark plug will fire on compression stroke and the other spark plug fires on exhaust stroke. Both spark plugs will fire until camshaft position is identified by a successful camshaft sensor signal.

Engine Running

Once camshaft position is identified and engine is running, only spark plug with cylinder under compression will be fired.

CMP Failure Mode Effects Management (CMP FMEM)

During CMP FMEM, COP ignition operates similar to engine cranking mode. This allows engine to operate without requiring PCM to know if cylinder is on compression or exhaust stroke.

Fig 1: View Of Coil On Plug

Courtesy of FORD MOTOR CO.

RENDER: 1.0x

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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.