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david, Auto Service Technician
Category: Dodge
Satisfied Customers: 1500
Experience:  Certified Master Technician,Certified in diesel & gasoline engines
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I have a 2001 Dakota with 3.9l and A/T. There is a random misfire

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P301, P303, P305, P351
I have a 2001 Dakota with 3.9l and A/T. There is a random misfire code for all of bank 1. I have replaced ALL of the sensors on the engine, reman heads (a tech told me it was a bad spring) Lifters pushrods, well the only parts left are the "short block". I have tried new ECMs, I have new cats (California Emissions) new O2 sensors. I need some help, I am not the only one with this problem, it would seem that V6 + A/T gets a bank# XXXXX Sometimes the truck runs like a champ, but mostly it drags and gets 13 mpg.
Hi thank you for your question hope this helps.

P0351 = Ignition Coil #1 Primary Circuit Peak Primary circuit current not achieved with maximum dwell time.

P0305 = Cylinder #5 Mis-Fire Misfire detected in cylinder #5.

P0303 = Cylinder #3 Mis-Fire Misfire detected in cylinder #3.

P0301 = Cylinder #1 Mis-Fire Misfire detected in cylinder #1.

Lets bank these codes down and check them one at a time.
The P0351 could be the cause of the whole problem.

Most likely a voltage regulation or grounding issue. check the voltages coming off the alternator for at least a few minutes and watch for voltage spikes.

Start with the basics. check the battery ground and then the ground strap that goes from your chassis to the motor. since its 9 years old I bet there is corrosion/gunk on the motor ground strap. pull it off, clean all the surfaces and reinstall. then check the engine wiring harness grounds, consult your wiring diagrams in the repair manual to find those. The orange wire with the green stripe is a ground wire going to nearly every sensor and all injectors as well as the coil and many other things.

I would still check your voltage regulation, although it could probably be off because of a ground issue too.

Now for the random misfire code have you tried moving the bank 1 coils to bankXXXXXyou know if it is a coil problem.

Hope this helps
Good luck
Customer: replied 7 years ago.
I apologize for not mentioning earlier, but I have installed a Crane cams HI-6 ignition system, along with the P-91 coil. I also have iridium plugs because the regular champions were fouling out constantly on the #1 bank. I also replaced the distributor and cam position sensor because I was told that could cause a misfire.
The grounding issue I will look into, I bought the truck used and cleaned a golfball sized chunk of corrosion off both terminals. The positive battery cable is almost gone and I cannot stop the corrosion from coming back. Does the dealership sell only the battery cables. I asked locally and was told "no".
The motor ground strap is good, when I replaced the heads, I cleaned everything, and the truck ran flawlessly for about a week. Then it stalled at a light, and has had the codes ever since.
I will test the alternator-what voltages should I look for? Or will it be obvious that I have a problem?
Let me know about these things, I am going to accept after this reply anyway, but if at all possible I would like to contact you later if I can't figure this out. Thanks Chris J.
The dealer should be able to get the battery cables they will have to order them but it should be no problem. If not The best place to get battery cables is to find a place that can make them for you to order but they are getting hard to find. If you do not have a place that can do this, you can make your own just get the wire and a set of cable ends.

You should see 14v at the alternator with the engine running. the voltage should be the same as the battery with the engine off.

Yes it should be obvious that there is a problem.

You can contact any time just like you are now even after accepting. This question is open till you close it.

Let me know.
david and 4 other Dodge Specialists are ready to help you
Customer: replied 7 years ago.
I checked the voltage today, wild peaks on the alternator to block (5v - 14.01v) However the battery was a constant 13.9+/- .05 So that looks good I think (truck idled up and down just a bit) I am looking into finding the ground strap and any other corroded areas. How do I check the voltage regulator? I don't know what I'm looking for on this truck, and the Hayne's manual isn't very good for electrical diagnostics. Thanks, XXXXX XXXXX
Voltage Regulator

The (EVR) voltage regulating circuit is in the Power train Control Module (PCM) and is not serviced separately.






OK it looks like you are loosing milli volts passable some milli amps, between the alternator and battery. This could be bad connection at the battery or the alternator.


Try somthong check the voltage with the engine at about 1,000 RPMs.





"truck idled up and down just a bit" This could be the Throttle Position Sensor (TPS). Back feeding from the PCM do to a bad connection or the voltage drop.

Voltage in the newer cars and trucks is vary tricky because every thing is controlled my the computer.

Voltmeter Testing the TPS

A sensor can be tested with a voltmeter while its electrical wiring is still connected (this is called back probing a connector). Move the throttle slowly from closed to open. At different throttle openings, varying resistances are specified. Watch for any glitches.

  • With the ignition switch on, connect a voltmeter between the reference wire to ground.
  • Normally, the voltage reading should be approximately 5 volts.
    • If the reference wire is not supplying the specified voltage, check the voltage on this wire at the computer terminal.
    • If the voltage is within specifications at the computer, but low at the sensor, repair the reference wire.
    • When this voltage is low at the computer, check the voltage supply wires and ground wires on the computer.
    • If these wires are satisfactory, replace the computer.
  • With the ignition switch on, connect the voltmeter from the sensor ground wire to the battery ground.
  • If the voltage drop across this circuit exceeds specifications, repair the ground wire from the sensor to the computer.
NOTE When the throttle is opened gradually to check the throttle position sensor voltage signal, tap the sensor lightly and watch for fluctuations on the voltmeter pointer, indicating a defective sensor.
  • With the ignition switch on, connect a voltmeter from the sensor signal wire to ground.
  • Slowly open the throttle and observe the voltmeter.
  • The voltmeter reading should increase smoothly and gradually.
  • Typical TP sensor voltage readings would be 0.5 volt to 1 volt with the throttle in the idle position, and 4 to 5 volts at wide-open throttle.
  • If the TP sensor does not have the specified voltage or if the voltage signal is erratic, replace the sensor.
Sensor wire 1 and 3 go to the cam and crank sensors wire 2 goes to the PCM under lined in RED

Also check the ground continuity at the PCM pin 31 and 32

Let me know
Customer: replied 7 years ago.
I checked the grounds to the frame and block, and they are clean. The terminals I will replace tomorrow. The TPS reads .7 @ idle and 3.7 @ WOT. I will test it again after I replace the terminals, but it will probably be the same as I tested it from the sensor to the (-) post on the battery. I did not get a smooth rise in voltage from the sensor either. I also tried to test that c23 wire and I was unable to get a reading at all. I pulled apart the connector to make sure I was testing the correct wire, and I was. After I replace the terminals, should I go ahead and get a new TPS? Is 3.7 too low or is there a short I will have to find that is giving me this reading? Thanks so much, I really appreciate your help. Chris J.
OK this is a fun one, Got to love electrical problems can be fun to trace down.

Lets fix one thing at a time replace the terminals, I would recommend adding a another ground off the engine to the frame. Because the grounds were not so good on this engine.

Then test the voltage at the alternator and the battery. If all is good them test the TPS again.

I am hear to help fix the problem what ever it takes
Customer: replied 7 years ago.
i replaced the terminals, and the TPS and added a ground strap from the block to the frame. I still have the same voltages as before, except the alternator no longer spikes. It is at a steady 13.75v (+/- .02). I still can not get a reading from the #23 pin and the misfire is still there. When I give the truck gas there is a hesitation and a hissing sound, then a muffled "pop". This happens in less than a second. Then the truck will accelerate.
Ok good there was a bad connection problem got that fixed.

Now the alternator is not putting out the right voltage it should be putting out 14v to 14.5v. Anything under that the alternator is bad.

I think there was a little misunderstanding on pin #23. The TPS signal enters the PCM throw pin 23 there will be no reading from the #23 if the TPS is unpluged.
Are you getting a signal from the TPS?

Is this something new? "There is a hesitation and a hissing sound, then a muffled pop"
Customer: replied 7 years ago.
"Is this something new? "There is a hesitation and a hissing sound, then a muffled pop" "- New as in it started Sunday, It did it once before about 3 months ago, but I figured it was bad gas. Now it is happening after the truck has warmed up, then cooled down and run again. Only happens once and I can press the gas to the floor and it stops and does not happen again. So I need a new alternator... can I have mine tested @ Autozone, etc... will the test show a problem in the alternator? If I need to replace the alt. what size, 117 or 136 amp?
Yes Auto zone can test your alternator for free. I would go with the higher amp alternator just because It puts less strain on the battery and it will also last longer do to it not needing to run as hard as the 117 amp. Just me I like more power available.

This hesitation and a hissing sound leads me to think fuel or fuel injector problem.
With it only being on 1 bank the fuel is ok. So i would check into the injectors, This could also cause the misfire.

Have you had the injectors checked?

I think the hissing sound is the engine starving for fuel.

The pop is the unburnt fuel leaving the cylinder into the exhaust and igniting.
Customer: replied 7 years ago.
Wow, that isn't good. the injectors are only about 2 years old and I have swapped them from one side to the other with no difference in performance and I get the same trouble codes. I will get a alternator this weekend (and have mine tested).
Boy o Boy this is a fun one.

So it is not the injectors it is not the plugs it is not connections to and from the PCM injectors.

I would have to say you need to get the truck hooked up to a scan tool and watch what is going on with the engine in freeze frame. Most shop will do a diagnoses for cheap.
Customer: replied 7 years ago.
I got an alternator today from the boneyard. tested out fine on the machine. My old one failed on both amps and volts. I started the truck up after install, but I can't tell if there is a difference yet. It still idles pretty hard (whole truck shakes).

"Most shop will do a diagnoses for cheap."
How cheap is cheap, and where do you recommend? I want to watch them do the test, and have the codes explained as we go.

"it is not connections to and from the PCM injectors"
Are these the connections for the computer to "fire" the injectors? I tried to test them but if there is a difference in voltage it happens so fast I can't tell. A diagnostic will tell me this? And what exactly do I ask to be done to the truck. Is there a specific test I should ask for, like testing a motherboard on a computer. Run it 'till it crashes (stress test).
Customer: replied 7 years ago.
When I installed the new alternator, I get 13.6 volts.
My friend lets get another expert to tack a look at this and see if they see southing different.
Customer: replied 7 years ago.
I really appreciate your help, thank you. Sorry this is so frustrating, is there a specific diagnostic I need? I will get that done next week, and if you don't mind I'd like to let you know what they say. Thanks again for your help, Chris J.
Please yes tell me what they say.

You need to have the engine scoped just tell them what the truck is doing and that you need to know what the computer is doing.

The hard ones are all ways frustrating It would be essayer if I was there and could check it over and see what is what.

Good luck let me know what you find ok.
My friend

At the same time have them do a compression test on both banks.

I do not what to worry you but a another expert thinks it could be off-time camshaft on the left bank or something like a broken dowel on the cam. A compression test will tell the story if compression test on any cylinder compared to the right side is a Big difference = mechanical oops.

Good luck
Customer: replied 7 years ago.
That makes sense, I did a compression test and came up with some wild #s. I did the tests several times and the #1 bank always fluctuated by 20 - 50 psi on all three cylinders. I asked about it on here (or a similar ? site) as a matter of fact and was told that the engine couldn't run if it was that far off, must have done something wrong with the test. #2 bank was was all pretty close(within 10 psi or so). I was leaning toward a fuel timing issue (computer) but I think you're right about the cam. Would a new timing set fix that issue or would the cam need to be replaced.
My friend 20 - 50 psi fluctuated man I would pull the timing cover off and see how off it is.

First have you done a leek down test? This will tell you were the compression is going. Along with what the problem is.

Then pull the timing cover off and see were the timing marks are.

Then you need to pull the cam out and see how it looks.

Sorry about not seeing this before but I was looking for mechanical problems.

Let me know
Customer: replied 7 years ago.
OK, I can probably pull the motor apart this weekend. If I can find the gaskets, nothing seems to be locally stocked for these motors. How would I do a leak down test? If the cam is off, but the rings are still good what will I be looking for? There was still crosshatch on the cylinder walls when I replaced the heads, and I couldn't "feel" a lip on the top of the cylinder (although I'm sure one is there). Only the #2 cylinder had a line going down the cylinder wall, but it was just shiny and about 1/4" wide. No groove, even with a light shone on the wall there was not a transition line.
Would it be safe to go ahead and change the timing set anyway? 160,000+ miles. Also, should I replace the tensioner, or just the chain/ gears? Thanks, XXXXX XXXXX
Do the leek down test first before doing any thing. You are looking for were the compression (air) is going.

The leek down test will tell you if one of the valves is open (you will hear air coming out the intake or exhaust) This way you know it is the cam or valves.

If you hear a lot of air coming out the dip stick or oil fill hole (Think piston, valve guilds)

As for the block with 160,000+ miles on it every thing sounds ok.

Yes parts for the 3.9 are getting hard to find.

Let me know what the leek down test shows.
Customer: replied 7 years ago.
I bought the tester, but I have no idea how to get TDC on any of the cylinders. There are no marks on the pulleys that seem to reference crank position. There are marks at 90 degrees, but I have a v6 and they should be at 120 degrees.
I am at the point of giving up on this motor, and I hate giving up on anything... The fact seems to be that I have a mechanical issue with this motor, and fixing it would cost as much if not more than a v8 swap. I truly hoped that you would tell me that it was a simple wire that had come loose, and my truck would be fixed.
If you can tell me how to find TDC on my engine, I'll still do the test for purposes of knowing it was or wasn't this or that.
Thank you again for your patience with me and this problem. Chris J.
Easy way to find TDC remove one plug at a time say #1 now with your finger over the hole turn the engine over by hand till you feel the compression pushing your finger off now look down the plug hole till you see it is at the top of the stork.

Here is the firing order to help

My friend I was hoping it was something easy, Trust me we all have been there.

I hate giving bad news. Almost as much as I hate giving up on something.
Work the problem the engine is a hunk of steel it is not smarter then you.

Swapping in the V8 is a way to go but the V8 swap is not cheap. Think new transmission T case if 4X4 new PCM and all the wiring. "Big can of worms"

Let me know
Customer: replied 7 years ago.
for some reason I am unable to leave any feedback for you. I asked a question a year ago, and that is the only one I can find.

I am truly grateful for all of your help and if I ever have another question I will look for you personally. Thank you, XXXXX XXXXX
OK that is ok. Just knowing you are happy with me help is all I need.

Good luck