Test Procedure

JF1 DETERMINE WHICH COIL IS NOT FIRING PROPERLY

NOTE: Electronic ignition engine timing is entirely controlled by the PCM. Electronic ignition timing is NOT adjustable. Do not attempt to check base timing. You will receive false readings.

Determine which coil is not firing properly using the information from Pinpoint Test JB or a DTC and the table at the beginning of this pinpoint test.
Record the suspect cylinder, coil and PCM pin number from the table.

Have the suspect cylinder number, coil driver and PCM pin number been recorded?

Yes	No
GO to JF2.	REPEAT the test step to obtain the required information.

JF2 CHECK THE FUNCTIONALITY OF THE SUSPECT COIL DRIVER CIRCUIT

Suspect Coil connector disconnected.
Connect a non-powered test lamp between the IGN START/RUN and suspect coil driver, harness side.
Disable the fuel pump by disconnecting the inertia fuel shutoff switch.
Observe the test lamp while cranking the engine.

Is the test lamp blinking consistently?

Yes	No
Key in OFF position. GO to JF3.	Key in OFF position. GO to JF4.

JF3 CHECK THE FUNCTIONALITY OF THE SUSPECT COIL

Carry out a visual inspection. Closely inspect the coil case and boot for carbon tracking, cracks and torn or improperly installed boots.
Remove the suspect COP from the spark plug.
Connect the air gap spark tester 303-DO37 (D81P-6666-A) or its equivalent in series between the suspect coil tower and the spark plug wire.
Suspect Coil connector connected.
Observe the spark tester while cranking the engine.

Is a bluish-white spark present?

Yes	No
Key in OFF position. GO to PINPOINT TEST Z STEP 1 .	Key in OFF position. INSTALL a new Suspect Coil. If necessary, INSTALL a new spark plug.

JF4 CHECK IGN START/RUN VOLTAGE TO SUSPECT COIL

Key in ON position.
Suspect Coil connector disconnected.

Measure the voltage between:

(+) COP Connector, Harness Side	(-) Vehicle Battery
IGN START/RUN	Negative terminal

Is the voltage greater than 10.5 V?

Yes	No
Key in OFF position. GO to JF6.	Key in OFF position. GO to JF5.

JF5 DETERMINE THE VEHICLE BEING DIAGNOSED

Are you diagnosing an LS, Crown Victoria, Grand Marquis, Mustang, Thunderbird or Town Car?

Yes	No
GO to PINPOINT TEST B STEP 4 .	REPAIR the open circuit.

JF6 CHECK THE SUSPECT COIL DRIVER CIRCUIT FOR AN OPEN IN THE HARNESS

PCM connector disconnected.
Suspect Coil connector disconnected.

Measure the resistance between:

(+) PCM Connector, Harness Side	(-) COP Connector, Harness Side
Suspect coil driver.	COP

Is the resistance less than 5 ohms?

Yes	No
GO to JF7.	REPAIR the open circuit.

JF7 CHECK THE SUSPECT COIL DRIVER CIRCUIT FOR A SHORT TO VPWR IN THE HARNESS

Key in ON position.

Measure the voltage between:

(+) PCM Connector, Harness Side	(-) Vehicle Battery
Suspect coil driver.	Negative terminal

Is the voltage less than 1 V?

Yes	No
Key in OFF position. GO to JF8.	Key in OFF position. REPAIR the short circuit to PWR.

JF8 CHECK THE SUSPECT COIL DRIVER CIRCUIT FOR A SHORT TO GROUND IN THE HARNESS

Measure the resistance between:

(+) PCM Connector, Harness Side	(-) Vehicle Battery
Suspect coil driver.	Negative terminal

Is the resistance greater than 10K ohms?

Yes	No
INSTALL a new PCM and retest vehicle. REFER to FLASH ELECTRICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY (EEPROM) . If the concern or DTC is still present, GO to JF9.	REPAIR the short circuit to GND.

JF9 CHECK THE SUSPECT COIL FOR DAMAGE

PCM connector connected.
Connect the air gap spark tester 303-DO37 (D81P-6666-A) or its equivalent in series between the suspect coil tower and the spark plug wire.
Locate and activate the fuel inertia switch to disable fuel pump.
Observe the spark tester while cranking the engine.

Is a bluish-white spark present?

Yes	No
Key in OFF position. If necessary, INSTALL a new spark plug.	Key in OFF position. INSTALL a new Suspect Coil.