Good afternoon,

I'm glad I found this forum - lots of great information. I have a 2002 Ford Escape, 6cyl FWD... 110,000 miles.

About a month ago I started seeing a misfire, which of course usually is a COP issue. I should buy stock in whoever makes those. Anyway, the code according to parts store monkey was cylinder 2 misfire, so I replaced the COP. That made no difference. I also replaced the upper intake gaskets and the PCV valve while I was in there.

So I started monitoring when it would happen, and of course got the actual code rather than taking the word of the monkey at the parts store. The code is P0352 Primary / Secondary circuit malfunction.

Ruh Roh.

So after some research I find it could be the harness, it could be the PCM. The question I have is this misfire seems to only be when the motor is started after it's hot. What I mean is I can drive to work 10 miles, no problem. I can drive to Orlando 100 miles away - no problem as long as I don't stop on the way. The only time the misfire happens is when I start the motor when it's hot. So if I drive 10 miles to the store, then drive home before the motor cools completely I'll be coming home on 5 cylinders. If I wait 2 hours between stop and start I never have a misfire.

Does that jive with a true electrical problem? I'm no expert, but I don't understand why driving for 100 miles is fine, but 10 miles, stop start and 10 more is an electrical problem. I'm sure I'm sounding stupid to the experts... feel free to roast me.

I would appreciate any help, and I'm happy to provide any info needed.

 

Sooooo I had a shop check it out and indeed PCM is toes up. So I found a used one that I will have flashed, but the next question is do I dump $360 into 5 more new COPs? It seems like not, since the shop I had this tested at was not going to replace them, but I figure I would ask.

 

If it was me I would at least replace the back 3 if its apart if not i might see whats what with the new pcm.If you do remove intake again I would put new lower manifold gaskets on.I assume you installed new sparkplugs make sure there oem I thought there was issues with the wrong sparkplugs could damage coil packs

 

Thanks - absolutely I replaced the plugs, and good advice I went ahead and did the back 3. I also replaced the gaskets.

However.

I bought a used PCM, had it flashed today, installed it - same problem.



So since it's the same P0352 I'm guessing the next possibility is the harness is bad? Maybe a bad wire between COP 2 and the PCM?

 

Well, it seems like the harness connector at cylinder 2 might be the cause. I hooked up a voltmeter and powered on, indeed I have 12 volts. Wiggle the harness and the voltage drops.

Can I just cut the wire and replace it from the PCM to the COP or do I have to replace the whole harness?

 

It's yours to modify as you see fit. You may be able to find the bad spot in the wire that has frayed or flexed too much causing the wire to break, and just patch in there. I'd use a soldering iron to be sure the wire stays connected.
When I read your first posts, I figured you had some 'thermal creep' going on that made/broke the connection as it heated and cooled. You may need to replace the connector at the COP. Pigtails with the connector and ~6" of wire are available from FoMoCo, or a boneyard may allow you to snip-snip.
tom

 

Thanks - I will take a look at the replacement connector.

I've been through the COP and the plug just to triple verify that they were good - the are. So The connector to the COP has 2 wires - for cylinder 2 there is a purple/green which seems to be a contant 12volts. My question is what's the other wire? Is that a ground or some kind of control wire?

I assumed it was a ground, but then if it's a ground how does the PCM communicate with the COP?

 

These are some sources:
Buy Motorcraft Parts Online | Official Motorcraft Auto Parts Site | FordParts.com
or here:
Buy Motorcraft Parts Online | Official Motorcraft Auto Parts Site | FordParts.com

or maybe the starting link here:
https://www.ford-trucks.com/forums/3...ml#post2096739

Or an off the wall{non-factory}:
Automotive Electrical Connector Pigtails, Terminals, Tools and More

Some places to look.

tom

 

This may not be very helpful. Something you could look into is the wiring at the connector. It's been a while, but I recall a post or two about some stressed wires somewhere causing a code to be thrown (I think at the PCM connector). Sorry I can't be more specific.

 

I just read of a crankshaft position sensor that was causing problems. Seems the insulation on the wires was working its way up away from the connector, and allowing the wires to short against each other. Worth a look.
tom

 

I'll keep that in mind about the crankshaft sensor tomw - thanks.

I will recheck the connection at the PCM. One thing I can't figure out is there are 2 wires on the COP connector - a purple wire with a green trace, and the color of the other one escape me at the moment... but anyway I can find the purple wire with a green trace at the PCM, but the other wire (I'm assuming the ground) I can't find at the PCM.

Do you know if the ground goes all the back to the PCM or does it terminate elsewhere?

 

The COPs are provided power when the key is on. They are provided ground by the PCM. When the ground is interrupted, the COP collapses its magnetic field, and generates a bit of high-voltage electricity. It is the collapse of the field causing 'lines of force' to be cut, thus inducing the spark current.
Main point is that the computer controls the ground, not the power side of the circuit, so it does NOT have to flow all the juice to run the coils, just connect, and disconnect the flow from ground. It does not source the flow.
That said, each wire 'pair' to the COPs is color coded differently in the one (2003?) diagram I happened to download from the library. There is no 'common' color for the wires, they is all be different...
tom

 

Thanks again tomw - great information.

I will take a good look at the ground wire tonight.

 

This diagram confirms pin 52 is indeed for the Cylinder 2 COP, but I still can't find the ground. I see a bunch of grounds, pin 51 for example, but it's black. I'm not seeing a clear relationship between the circuit and it's ground. The ground from the Cylinder 2 COP looks light yellow with a violet stripe, which I can not find at the PCM connector.

I'm guessing a continuity tester is the only way for me to confirm which ground at the PCM connector corresponds to the ground of COP 2?

I should have taken an electronics course in college.

 

Pin 52 is the 'control' for the #2 cylinder COP. It controls the COP by providing a ground to allow current to flow into the coil, and then removing the ground. Internally, there is likely a transistor controlled by the logic & related 'stuff' to flow current to ground, and then stop flowing. The ground internal to the computer is connected to the body/engine/battery ground via multiple pins, perhaps even the case surrounding the board. The transistor that does the work for #2 is connected to pin 52, and to ground internal to the case.
tom