Hello,
Trying to help my daughter repair her (new to her) ford escape. Cylinder 1 is completely dead and will not fire at all. Coil is good (coil on plug), spark plug is good, etc. So I’ve gotten as far as this.
The connector for the coils is a two wire connector. How it should be, and how it is on cylinder 2-6, is a two wire connection, one is a switch wire, the other is on 12v at all times when the ignition is turned on. The switch wire should pulse 12V when you crank, and again, all other cylinders do this as they should, but cylinder 1 shows voltage at all times on both wires, one being a little weaker than the other. I tested with a circuit tester, so I don’t have the exact voltage, just know the light came on. Any ideas?
It sounds like the power train control module isn’t switching the ground on and off for coil #1.
Tester
Other ideas, the trigger-signal wire from the PCM to the coil (CDA to C111 in diagram above) isn’t making a good connection. Or the spark plug is shorted. Or the coil is faulty. How did you determine the no. 1 coil is good?
This type of problem is often sorted by an experienced tech using a lab o-scope to view & compare the signal voltages vs time. .
Did anything unusual occur just prior to noticing the symptoms? If there’s a PCM internal fault, most likely cause would be an overcurrent on that channel, maybe by probing that connector w/engine running? Or by a static shock.
I measured resistance across the two pins on each of the coils, and they all read the same, about 2.3 ohms. I also tested all of the coil connectors without them being plugged specifically to isolate the coil.
This issue popped up as intermittent for a day, and then the next day it wouldn’t start. Two different coils were replaced, and all the plugs, because they were due and might as well, but afterwards, the dead cylinder remained, but is no longer intermittent.
Is this something I could diagnose with a multimeter, probing the corresponding connections from the PCM with ignition in the “On” position, and if it’s still not switching at the PCM, does it warrant a replacement at that point? I’ve never had to mess with issues like this before, so I’m inexperienced when it comes to the different computer modules in a car.
Determine which pcm wire is the 12v signal to the coil and which is the trigger to ground. Back probe the wire while still connected to the pcm. If the trigger wire is 12v, pull that pin from the connector and measure it. If it is 12v, there is a short to positive between the coil and pcm. If the pcm pin reads 12v, you have a bad pcm.
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[quote=“Kinjorskii_185151, post:4, topic:190482”
I measured resistance across the two pins on each of the coils, and they all read the same, about 2.3 ohms. I also tested all of the coil connectors without them being plugged specifically to isolate the coil.
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You were correct to unplug the coil before measuring the winding resistance. The 2.3 ohm is the resistance of the low-voltage part of the coil windings, which sounds correct. There could still be a problem with the high voltage windings. You might be able to measure the high voltage winding resistance by probing from pin 2 to the connection that goes to the tip of the spark plug. Refer to schematic above.
Both the low & high voltage windings could measure the correct resistance, but the coil could still be faulty. To confirm the coil is good, swap it with another coil that is working correctly . If misfire moves to that cylinder, the coil is likely faulty.
