No communication between ignition coil and PCM

I hope someone can help because two mechanics can’t figure out what’s wrong. We have a 2010 Dodge Grand Caravan SE, 3.3L engine. One day out of the blue it wouldn’t start. There were NO warning signs. When turning the key, it cranks but won’t turn over. (It’s not the clicking sound of a dead battery, it sounds like it’s about to start but won’t finish turning over.) Our regular mechanic says there’s no communication between the ignition coil and the PCM but doesn’t have the ability to run diagnostic tests (small business). Another mechanic said it was the fuel pump… Guess what, we had it replaced and it’s not. Lengthy Google searches indicate that for most parts there are warning signs that it’s going out. We had none. One day it just wouldn’t start. We have an appointment with the dealership but it’s taking a month to get us in so I’d love to hear any suggestions anyone has… Maybe someone has run across this before? We are at our wits’ end.

Have they checked for a bad crankshaft position sensor?

https://www.justanswer.com/dodge/gzzkc-no-signal-coming-pcm-coil-control-2007-dodge-grand.html

Tester

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I mentioned it, but they said it would throw a code if it was bad.

Read what the article says about the Check Engine light.

Find a mechanic that knows what they’re doing.

Tester

Thank you. Definitely worth checking!

Tester is correct and I will just say there are other components that can fail and not leave a trouble code.

The problem here is that we do not know what is missing; fuel pressure or spark. Not knowing can run the number of potential problem areas way up.

Since the dealer is a month out, I might ask whether or not you have even a small amount of mechanical aptitude? Since this came on suddenly (and not knowing how the prior mechanics came to conclusions) I was going to suggest purchasing a cheap test light (5 dollarish) and test every fuse; both in the underhood fuse box and the dash fuse box.

Believe it or not, many vehicles have gone through a lot of expensive parts and tow bills when the cause was a 25 cent fuse.

Your mechanics need to prove their diagnosis. Other people here canj probably add to what I say: my 1996 Miata would not run the fuel pump, but the problem was that its ground was established in the ECU, and the ECU had failed. I found a rebuild service, and the rebuilt ECU fixed the problem. Thus, a very good look at power and ground to the fuel pump might help.

A tip about car repair nomenclature. When speaking to mechanics, tell them the engine “cranks ok with key in start, you hear the rrr rrr rrrr sound, but it won’t start”. “Turns over” is an ambiguous term and might cause confusion, at your expense.

When an engine clicks or nothing is heard at all, with key in "start’, that’s called a “no crank” problem, or “fails to crank” problem.

“Cranks ok but won’t start”, when that symptom happens suddenly and for no apparent reason, usually the cause is either no spark, or no fuel. The first step towards the solution is to figure out which of those it is. It will prove very difficult to solve this problem until you know which of the two it is. Suggest not to approach this by replacing parts, easy to run out of money before running out of ideas what to replace next.

Ask your shop to describe how they plan to figure this out, the no-fuel vs no-spark problem? Visual check for spark at tip of spark plug during cranking, o-scope test for hv current to spark plugs, measuring fuel rail pressure, testing if fuel injectors are being pulse, those are all common methods. Common sense says to also take advantage of the car’s built-in diagnostics, checking for diagnostic codes etc. You paid for those when you purchased the car, so might as well use them. As posted above, the built in diagnostics may not be able to tell you what you want to know, faulty crank sensor often produces no diagnostic code, but since it takes very little time to check for codes, still worth checking.

Yes, I was on the road and the car stalled. I was towed in to a shop. As they were diagnosing the problem, they said everything was dead. They came back a little later and said the crank sensor had come apart.

I still think how I phrased it is fairly accurate. If you think of starting a car as producing two sounds (when you turn the key in the ignition vs. when the car starts so you can let go of the key in the ignition for it to run), it does the first part but not the second.

In any case, you’ve given me some things to think about. Thank you!

I don’t know where this terminology comes from, but an engine has a crankshaft with pistons connected to it. It rotates which is why the term rpm or revolutions per minute is used. To start an engine it has an electric motor that rotates the engine or cranks the engine or turns it over. Cranks come from the time cars had a crank instead of a starter motor and you would physically insert the crank and give it a turn to start the engine. That’s why it makes no sense to say it cranks but doesn’t turn over.

Some people say cement too for concrete but cement is a component of concrete like sand and gravel. Then there is there, they’re, and their, or to two and too, all with different meanings. Just trying to help not sound uninformed.

No worries. I expect the majority of mechanics will understand what you mean, or will ask you to clarify if they don’t.

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Sure, there are just some things that are indicators of ignorance that sometimes you don’t want to let on. Like when my fuel injected car wouldn’t start and an old duffer on a bike told be to pump the gas. Instant indication the guy knew nothing. Then use the wrong word in a written document and it is an immediate indicator.

An engine “turns over” when the starter is cranking the engine. Once the engine “fires” it is running under its own power. Period,end of story.

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"Doohickey, . . old mopar guy
I still think how I phrased (“it cranks but won’t turn over”) it is fairly accurate.
[/quote]
Take a look at the OPs screen name that would explain it. :roll_eyes:

When those cranks but won’t turn over words come into play it can be a bit irritating when it involves a repair order and the service advisor can’t clarify it.

Example. Got a repair order once that stated “Won’t start when driven as far as Dallas” which is roughly 400 miles round trip. The car out in the lot would fire right up every time and the service advisor had failed to ask for clarification from the customer who was now gone out of state for the next few weeks. The SA had also failed to get any contact info for that person.

I told the SA I would be glad to drive it to Dallas and back as long as I’m on the clock…

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Hey, I’m a 47 year old woman. I’m super handy but I’m not a mechanic. Let’s call it crank no start then. Let’s get past the terminology and move forward with this.