I have a 1995 Dodge Ram 2500 V10 and cylinders 5 and 10 which are the rear two are not firing. I have replaced ignition coils along with plugs and wires. Also, I have read codes, and all it says is there is misfire in one or more cylinders. Very helpful. Anyone know?
Are you getting misfire codes on cylinder 5 and cylinder 10 or are the 2 rear cylinders misfiring?
hmm the codes just said misfire on one or more cylinders i did a timing light to find out 5 and 10 were not firing which are the back two.... or do I have wires wrong?
Here.
I dont have wires wrong.. i believe 5 and 10 were not firing which i thought were the back two i will have to check it again. does it matter if it is the back two or 5 and 10 on how i would fix it?
do you have any idea how to fix it? my idea would be the ignition control module?
The reason I wanted to know if it was 5 and 10 is because, as you can see from the last diagram I posted, they share the same coil in the coil pack.
Yes, but i replaced all the coil packs so it must be whatever is controlling the coil packs which is where i come to the ignition control module
https://repairpal.com/ignition-control-module number 2 is EXACTLY what my truck is doing as far as misfiring and running rough
Wilson, I found the 1,700 page 1995 Ram Truck 1500-3500 Service Manual online (free)
You may want to download it.
Here's the link:
https://drive.google.com/file/d/0BwDkuRJfDNZEVVdHRkVFeTNmVUE/view
On page 386 it describes your ignition control module
Interesting stuff..
IGNITION CONTROL MODULE TEST—8.0L V-10 ENGINE
The ICM is located in the engine compartment. It is mounted to the right inner fender behind the cool-
ant reserve/overflow tank.
Ignition coil ground path circuits for paired cylinders number 1/6, 3/2 and 9/8 are operated by the PCM only.
A separate ignition control module (ICM) along with commands from the PCM, is used to control the ground path circuits for only two of the five paired coil packs. This will be for paired cylinders
number 4/7 and 5/10.
Wow... that explains a lot... I will pull out the timing light once more, but that would seem to be the problem then... because it controls 5 and 10 which are the ones that aren't firing.
But if the PCM controls the ICM then which one is bad? I would think the ICM because everything else on the truck is working so how would the PCM be bad?
Plus, if the PCM was bad, then the three coils that it controls wouldn't be firing. Right?
Maybe at this point, get an inline ignition spark tester and test each coil tower for spark.
If they're getting spark then they're getting a ground signal from the PCM/Ignition control module.
If any aren't getting spark, check the wire connections going into the coil pack connectors. (they're carrying the ground signal from the PCM/ICM to the individual coils in the coil pack to fire the spark).
If you're still concerned if both your PCM and ICM are providing ground signals to the coil packs, there's a useful diagram on page 387 of the Service Manual.
(I gotta say, the wiring diagrams in that manual alone are worth you downloading it)
It shows the pinout connections of both coil pack connectors.
You can test if the ground signals are coming from the PCM and ICM and determine if they are functioning.
When testing computer grounds it's best to use an LED Test Light and not one with a regular bulb.
You should test the B+ connections with a multimeter to determine exact voltage.
So when performing this 1st test you can either "back pin" the connections with a T-pin while they're plugged into the coil packs or you can disconnect them from the coil packs and test them from the front. Just be careful not to push the test light's probe into the connector and damage the sockets. Making contact is good enough.
So, looking at the diagrams, both coil pack connections have B+ (Battery Voltage) (12 volts+-) pins on them.
To test the B+ connections
- With the Coil Pack connected or not, it doesn't matter.
- Put your multimeter in Volts DC mode.
- Probe the power socket of the connector with the RED test lead of the multimeter.
- These are the B+ pins shown in the diagrams.
- Connect the black multimeter test lead to the battery Ground terminal.
- Have your assistant crank the engine.
- You should see the multimeter registering Battery voltage (12 Volts+-) while the engine is cranking.
If that checks out you can move on to testing the PCM/ICM ground signals and you can use these B+ socket pins for your positive battery voltage.
To test the Ground Signal Wires From The PCM/ICM
So the rest of the wires going to each coil pack are individual Ground Signal wires for each coil from the PCM/ICM and the test of all of them is the same.
- Disconnect the Coil Pack from its connector.
- Insert the probe of the LED test light to the power terminal of the connector (The B+ terminal in the coil pack socket you just tested).
- Attach the negative wire of the LED test light to any of the other (ground signal) terminals. (if your LED test light has an alligator clip, just use a T-pin in the clip and probe the ground signal terminals with the T-pin BUT BE CAREFUL, you can't let the T-pin on a computer ground touch the positive probe of your LED test light.
- Have your assistant crank the engine.
- One of 3 things will happen.
- The LED test light should flash if it's getting a ground signal from the PCM/ICM (Good PCM/ICM signal)
- The LED test light didn't flash. (No PCM/ICM ground signal reaching the that particular coil in the coil pack) (check wiring between PCM/ICM for breaks. (we hope)
- The LED test light stayed on (didn't flash). There may be a short to ground in the wiring between the Coil Pack and the PCM/ICM. (we hope)
- If you don't have ground signal and you can't find a wiring/connector issue then it's time to start suspecting a PCM/ICM issue.
What would you do at this point. It is narrowed down to just two things. A 400 dollar part or a 100 dollar part.
Stop replacing parts without knowing the problem.
I'm still not sure if we're talking about misfires in cylinders 9 and 10 or in cylinders 5 and 10.
Either way, put a spark tester on the coil towers of all the cylinders and determine which ones aren't firing.
If you confirm that there's no spark at any particular coil tower(s), test the PCM/ICM Ground signal to those coils.
I hope that lengthy instructional explanation I posted didn't discourage you from testing for a computer ground signal at the coil connections. You're just taking an LED test light, touching the probe to battery positive and the ground side to the coil input you're testing (on the coil pack), and cranking the engine.
While cranking the engine the LED should flash.
So if that happens, and you have no spark on one of the coils in the coil pack, then you have a defective coil pack. If you recently replaced it and bought it from one of the chain auto stores, it's probably under warranty.
Just put an inline ignition spark tester ($8 bucks) on each coil tower and watch for spark.
If you find any coils not producing spark, just test that particulars coil ground signal wire
I did check if i had a signal coming to the packs, I also checked with a timing light to see which ones weren't firing and like I said the only cylinders not firing are 5 and 10, which I know both are not in the back. with a test light, i found the wires coming from the PCM to the ICM a couple of them didn't have any power, let me see if i can draw out a diagram to post
how do I post a diagram i drew out in paint?
upload it to https://postimages.org/ and attach the link to your post
https://postimg.cc/KKGMLfkp/7a16d090 this is the plug going into the ICM from the PCM is all of that normal?
OK. Bear with me, I'm trying to keep up.
You did the ignition spark test on the coil packs.
You found that you aren't getting spark at the coil packs for cylinders #5 and #10.
They share the same coil in the, smaller (rear), coil pack so only 1 wire delivers ground signal for that coil in the rear coil pack for both #5 and #10 cylinders.
(We know that coil is betting B+ voltage because the 2nd coil in that coil pack which controls cylinders 8/9 is working.
This wire:
Have you checked the connector and followed that wire back to the ICM?
Maybe unplug it from the coil pack and from the ICM and check both ends of the wire for continuity to be sure there are no breaks/shorts in the wire?
I know for sure there are no breaks in the wire, the whole problem started when my dad and i were working on a fence because i live on a farm and he asked me to pull the truck over the hill and when i started driving that was the FIRST time it ever happened so it was kinda a very sudden thing. My dad then took it to a mechanic and he said he couldn't find anything wrong with it. Ha there is something very definetly something wrong with it. i checked the b+ and it had power but none of the other two had power but it only has misfire on 5 and 10. it is so confusing. i then checked the signal coming to the ICM from the PCM and that is where i got that diagram. did you see the diagram?
I did see the diagram. But without checking the wiring diagram you can't know which are power, lower voltage reference signals, or computer grounds so be careful probing those connections.
Let's discuss that rear coil pack.
The other 2 wires on that coil pack connector (besides the B+ wire) aren't power, they're computer grounds.
1 wire for each coil in that coil pack. They don't carry positive voltage.
The fact that you didn't find a ground signal when you tested the other computer ground terminal on that coil pack (for cylinders 8 and 9) means that you aren't doing your test right. The coil for cylinders 8/9 can't possibly fire without a ground signal from the PCM. You didn't find one but the coil is firing.
So something isn't being done right.
You'll know you are performing the Ground Signal wire test right when you're seeing the flashes of your LED test light on the computer ground of the "working" cylinders 8/9 coil's connection in that coil pack as you crank the engine.
When you have that, repeat the test on the Ground Signal wire for the cylinders 5/10 coil in that same coil pack with confidence that you're reading an actual absence of signal.
You're chasing down an electrical issue. You have to start at the load (which in this case is the coil pack) and then after eliminating issues there, move farther back towards the PCM/ICM.
i just dont get it... it is very hard to know what you are talking about without looking at the truck at the exact same time i am reading this
my head about to blow. im about ready to give up. i love everything about the truck exept it does not run right.............................................................
Okay, I've just discussed this with my dad and have shown him our discussion here on the forum. He said he thinks I do not fully understand what a ground signal is, as opposed to the power I would find on the B+ lead of the coil pack wire. He said he'll try to help me with the tests again tomorrow. One problem is that I do not yet have a LED test light, I just have one with a regular bulb. Dad says I need to thank all of you for taking so much of your time to help a 12 year old kid with a complicated problem. Thank you. I do appreciate it. Hopefully you'll hear back from me soon after we do more testing. Why can't Dodge build these trucks more like a Farmall H?
Let us know how it works out.
The PCM controls all the cylinder's firing.
What's interesting is that the PCM only goes through the ignition control module to control firing of cylinders #'s 4,5, 7, and 10.
The point being if your 2 most rear cylinders are misfiring, those cylinder #'s are 9 & 10.
According to the Service Manual, cylinder #9 isn't controlled by the ignition control module, it gets its firing signal directly from the PCM
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I am going to go check it with the timing light again. I don't remember if it was the rear two or not.
So 5 and 10 are the only ones not firing, but, when I rev the engine or try to make it work, the check engine light then comes on, and it sounds like it is running ever rougher. But even when that happens, I still have spark on every cylinder besides 5 and 10. Then when I shut the truck off, and turn the truck back on, it resets the computer and the check engine is off again. Not sure why that is, but the only cylinders not firing are 5 and 10. Am I allowed to post videos on this forum? If I could then I would send a video.
@WilsonFink yes you can make a video but we recommend you upload to YouTube and then post a link here.
Did you ever find a resolution to this problem my 95 2500 v10 is doing the same thing
Take a look at the misfire topic in our FAQ
If this engine has roller lifters, you might want to pull the valve covers, have someone turn the engine over and watch the movement of the rocker arms to see if they are uniform or if some are not moving correctly through their cycle. If this is the case, you'll have to pull the heads and replace the cam and the roller lifters with some after market quality parts.
