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Diagnostic Aids

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Perform this test when instructed during QUICK TEST or if directed by other test procedures. This test is used to diagnose the following:

    NOTE: Performing TEST JB  and using test results can help determine which coil is not firing.

  1. 1) Determine Which Cylinder Is Not Firing
    Using engine analyzer, ignition coil-to-cylinder correlation chart and illustrations, determine which coil is not firing. See Fig 5. Record cylinder, coil and PCM connector pin number(s) and go to next step.

  2. 2) DTC P0351, P0352, P0353 & P0354

    Disconnect suspect coil that was determined in step 1)  . Turn ignition on. Measure voltage between IGN START/RUN terminal at coil wiring harness connector and negative battery terminal. See Fig 1-Fig 5 . If voltage is more than 10 volts, turn ignition off and go to step  5). If voltage is 10 volts or less, check condition of related fuses/fuse links. If fuse/fuse links are blown, check for short to ground in IGN START/RUN circuit. Repair as necessary. If fuse/fuse links are okay, repair open in IGN START/RUN circuit.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 2) to step 5). No test procedures have been omitted.

  3. 5) Check Functionality Of Suspect Coil Driver Circuit

    Connect a test light between IGN START/RUN terminal and suspect CD circuit terminal at coil wiring harness connector. Disconnect Inertia Fuel Shutoff (IFS) switch to disable fuel pump. Observe test light and crank engine. If test light blinks consistently, turn ignition off and go to step  11). If test light does not blink consistently, go to next step.

  4. 6) Check For Open In Suspect CD Circuit

    Disconnect PCM connector. Measure resistance of suspect CD circuit between PCM connector and appropriate coil wiring harness connector. See Fig 5. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in CD circuit.

  5. 7) Check For Short To Power In Suspect CD Circuit

    Turn ignition on. Measure voltage suspect CD circuit between appropriate pin at PCM connector and negative battery terminal. If voltage is less than one volt, go to next step. If voltage is one volt or more, repair short to power in CD circuit.

  6. 8) Check For Short To Ground In Suspect CD Circuit

    Disconnect scan tool from DLC. Measure resistance of suspect CD circuit between appropriate pin at PCM connector and negative battery terminal. If resistance is more than 10,000 ohms, go to next step. If resistance is 10,000 ohms or less, repair short to ground in CD circuit. After repair is complete, go to step  10).

  7. 9) Check For Intermittent Fault

    Connect DVOM between D circuit pin at PCM connector and CD terminal at coil wiring harness connector. Observe DVOM for indication of fault while wiggling and bending suspect CD circuit. Start at coil connector and work toward PCM connector. Fault will be indicated by sudden change in DVOM resistance. If a fault is indicated, isolate fault and repair as necessary. If no fault is indicated, replace PCM.

  8. 10) Check Suspect Coil For Open Circuit

    Measure resistance of suspect coil between CD terminal and IGN START/RUN terminal at coil wiring harness connector. If resistance is less than 5 ohms, coil pack is okay. Testing is complete. If resistance is 5 ohms or more, replace coil pack.

  9. 11) Check Suspect Coil For Open Circuit

    Measure resistance of suspect coil between CD terminal and IGN START/RUN terminal at coil wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, replace coil pack.

  10. 12) Check Coil Secondary

    Disconnect both plug wires from suspect coil. Measure secondary resistance of coil between coil pack towers. If resistance is not 12,000-14,500 ohms, replace coil pack. If resistance is 12,000-14,500 ohms, coil is okay. If DTC P0350 is present, go to TEST JB . On all others, go to TEST Z .
Fig 1: Identifying 4-Tower Coil Pack Wiring Harness Connector Terminals (Contour 2.0L, Cougar 2.0L, Escort, Mystique 2.0L & Tracer)
G99E02628Courtesy of FORD MOTOR CO.
Fig 2: Identifying 4-Tower Coil Pack Wiring Harness Connector Terminals (Econoline 4.6L, Expedition 4.6L, Explorer 5.0L, Mountaineer 5.0L, Pickup 4.6L & Ranger 2.5L)
G99I02630Courtesy of FORD MOTOR CO.
Fig 3: Identifying Horizontal 6-Tower Coil Pack Wiring Harness Connector Terminals (Ranger 4.0L, Explorer 4.0L & Mountaineer 4.0L)
G99C02632Courtesy of FORD MOTOR CO.
Fig 4: Identifying Vertical 6-Tower Coil Pack Wiring Harness Connector Terminals (Contour 2.5L, Cougar 2.5L, Econoline 4.2L, Mystique 2.5L, Mustang 3.8L, Pickup 4.2L, Ranger 3.0L, Sable 3.0L, Taurus 3.0L & Windstar)
G99G02634Courtesy of FORD MOTOR CO.
Fig 5: Ignition Coil-To-Cylinder Correlation
G98G00220Courtesy of FORD MOTOR CO.
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