Code p0353

checked compression ranged 100-120 psi. the 100 I think was low because I don't think I had the hose connected all the way. But that limited another thing on the possible cause for the code list. Also got another coil told them that the first one I got was a possibly bad and it is running a tad worse then with my previous new coil. I think I need to check resistance in the wires between the PCM and the coil.

Checked the wires between coil and computer all resistance was .3 ohms, so all good.

Those compression numbers are pretty low.
You need to test compression with all spark plugs removed, and throttle plate propped open.
Starter motor just can't spin crank fast enough with only 1 spark plug removed.

While low compression can cause a misfire it wouldn't give you that code number.

You have eliminated or tested most of the possible causes.
Wrecking yards are full of computers, you need one that matches your setup, engine, and trans.
Don't know if there is a PCM cross-reference table, wrecking yard might have access to one.

RonD said:

Those compression numbers are pretty low.

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Yes they are. Did you do the compression test with engine hot? You also need to disconnect the fuel pump (pull fuse) and start the engine to release the pressure before the comp. test.

For reference my compression numbers done just last month are 185-195. Also keep track of compression on each cyl'd.

I think the computer records a miss based on rotation timing from the crank sensor??? I'm not sure it can detect electrical miss or mechanical miss. Need a techy to confirm. A week compression in one cyl'd will put the timing off on that cyl'd.

Yes, crank sensor is used to detect miss, crank sensor "sees" it the same way you feel it, missing rotational power.
That's why you never get a miss detected CEL going downhill only uphill or accelerating, lol

The P0353 code has more to do with the electrical side of things than just a detected miss, although a miss is the symptom.
Each time a coil fires(PCM lifts the ground to fire the coil) the PCM gets a feed back voltage on that now ungrounded wire which it monitors, the P0353 code means it's not getting the correct feedback.
Which could be a wire issue, a coil issue, or the driver circuit issue(in the PCM) that fires the coil.
Shorted/bad wire would be the most common reason, or bad connection at PCM or coil.

The transistors(driver circuit in PCM) that fire each coil can go bad

RonD said:

Each time a coil fires(PCM lifts the ground to fire the coil) the PCM gets a feed back voltage on that now ungrounded wire which it monitors, the P0353 code means it's not getting the correct feedback.

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That would be the 12v primary? If so then wouldn't #4 also show miss - same primary?

The waste spark system runs 2 spark plugs on 1 coil in the coil pack, to do that the spark plugs are connected in series, + to - to + to -
What this means is that 1 spark plug has a normal center electrode to ground electrode spark, but the other one has a ground electrode to center spark, reverse spark, but still a spark.
The reverse spark tends to be weaker.
But because of the temperature differences in the spark plugs on the compression stroke(cooler) and the exhaust stroke(hotter) most of the spark power goes to the least resistant spark plug, the cooler one, compression stroke, so in most cases the weaker reverse spark is not an issue.

The 12volts is always at the coil(key on), the ground path is used to allow voltage to flow thru the primary windings in the coil, this was the same setup that was used in the distributor and points system, "-" controlled the coil power.

If a coil dies completely, yes, 2 spark plugs will go with it, but if it is running out of spec then it might effect only one spark plug in the pair.
Could be the driver in the ignition module(PCM) limiting voltage at the primary coil so less spark voltage is available, or wire to coil(or connectors) is reducing voltage, or inside the coil there could be a problem.



For general P030x misfires it could be lower or higher resistance in one spark plug of the pair, this could be in the secondary windings in the coil or spark plug wire or spark plug.
When radios, and now sensors and computers, were added to vehicles solid conductor spark plug wires(0 resistance) had to go, too much noise and interference.

Higher resistance spark plug wires are used now to reduce this noise...and spark voltage.
Spark plugs can also have resistors built-in which are said to reduce noise but are really there to save the electrodes, not that it matters, lol.
On distributor setups resistance wasn't as much of an issue, one spark plug one spark, unless it got way out of spec.
With the waste spark system and knowing electricity travels to the path of least resistance and that two spark plugs are sharing the same path/coil............it can be a different story.
If one of the spark plugs or wires has higher resistance, then the other plug/wire will get most of the spark voltage each time coil fires, making for a weak spark in one cylinder.
This is easy to test for with an OHM meter, but heat changes things, so cold test won't always ID a problem.

So to erase any doubt of wiring issues I put jump wires in and bypassed the old wires. Figured it was an easy no cost way to eliminate on big possible problem. I also took out the connectors to the coil and adjusted them to be tighter and tested them and there is a good tight fit on all connectors there. I also took a paper clip that had a od that is small then the od of the PCM male connectors and put the paper clip in the corresponding female connectors and they are great fits too. I even checked in comparison of some of the other connectors in the female connection of the PCM and the ones for the coil seam to be the tightest fit.

Even with jumping the wires still got p0353 code.

I was wondering if the: PCM receives a bad signal from the coil and gives the p0353
or
PCM sends a bad signal to the coil

I don't know where I am going with that but I switch coil B and coil C wires and corresponding cables. So PCM says to fire B but it fires coil C and that fires B's plugs. And visa-versa for C wire.

I don't know what that is showing but it runs the same and I get the same code.

Any thoughts

Thanks for helping me through this.

I'll check OHMs for cables too. What should I be looking for in the numbers?

The PCM does both, it has 3 drivers that power on and off one coil each, the PCM also has the ignition module built in, it gets the Crank position signal and Cam position signal(if so equipped) and uses those to tell the drivers when to fire each coil.
It also monitors the feedback on the 3 coil lines.

From everything you have done so far I think you are down to an issue inside the PCM.
As said wrecking yards should have them.
Just as a note, look around the PCM for ground points, since the PCM controls pretty much everything by grounding it, loose or bad grounds at the PCM will be an issue.
I remember you mentioned wet area on the PCM, wet = rust, rust = bad ground.

Thanks for the idea Ron, cleaned grounds same-old-same-old. Bought a computer should be getting it soon. When I get it flashed at the dealership do I need both keys, that seems to be a controversy. Also do I need the whole vehicle there or can I just take in the computer?

Take all the keys you have, and get a 3rd added if you don't have one, once new PCM(PATS) is programmed with the key IDs you can add your own new keys IF you have 2 working keys.
Having a 3rd working key is a cheap insurance policy, people usually only lose 1 key at a time, so having that now 2nd key allows you to get another key without an expensive trip to the dealer.

You can check with the dealer but as far as I know the PATS system is in the PCM, only outside part is the Reader near the ignition switch which is just a "sensor" so doesn't need any programming with new EEC install.
So "should be" plug and play

New EEC will take 20-100 miles to learn all the sensor parameters, so don't panic if it's not perfect right away.

OK FINALLY got my new EEC this week, took forever, usually when it says 10 days to ship it does it in 3-4 not 12.

So I cheaped out and got one of a low mileage ranger off flee-bay. Said that it ran fine, so I went for the gamble. The compatibility chart said that it would work for my truck, same year and engine size so it should be good, hopefully.

So I want to make sure I understand what you are saying is that you don't think that I need to get the ecc flashed or anything. Nor do I have to worry about the key programing. I was looking at some wiring diagram and that is what I get to. Just assumed before. If I don't have to take this thing to the dealship it will save me some major $$$. And that make me happy, and makes me want to buy you a few beers RonD.

If you have PATS the new EEC(PCM) will need to be programmed unless they sent you keys with it.

As far as I know it does need to be in the vehicle, so they can plug in to the OBD port to program it.

But...... many locksmiths can provide that service now, so I would call around to check prices for mobile service.

My above point was to have 3 keys added to the new EEC(PCM) when you do it, because if you lose a key you can add another yourself if you have 2 working keys, so you must have 2 working keys to add a key yourself.

Thank God and thank you RonD for all the help my truck is running again. It took awhile to get an appointment with the lock smith for the keys because my schedule is hard to work with. Plus they told me twice that they could do it, so I scheduled an appointment in a week, when I called a couple of hours before the appointment to make sure everything was still a go they told me, "Well, maybe we can't do that" Then I had to get another person which cost me $60. The first people could of done it and it would of only cost $30. Oh well lesson learned, and I have my truck again so I am Very Happy. Thanks again RonD, God Bless

Good job in "gettin' er done"

Thanks for the words, and for posting the update