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New PCM but now crank, no start? 02 Dakota 4.7

4K views 18 replies 3 participants last post by  greenfieldhippi 
#1 ·
Hey all, first off hi I'm new to this forum and to owning a Dodge. There's quite a bit of backstory to my current situation but I'll try to make it brief.

Recently I acquired a 2002 Dodge Dakota RWD 4 door 4.7. It has only 45k miles on it and it had been sitting for a while. The original owner had it for a long while but never drove it when multiple years ago someone smashed his window while it was raining. After water got in the door panel the airbags went off. After that he let it sit for a while but it still started and ran but would die while driving.
Eventually he sold it to me for next to nothing because his mechanic told him it needed a PCM.

When I first acquired the vehicle it was throwing P0601 it idled fine, you could go into gears but would immediately die the second you let your foot off the gas if you tried driving.

So I bought a new PCM from a friend that was parting out the exact same truck. PCM numbers all matched.
Now the truck sat for about a month or two in between the time I got the truck to my place and bought a new PCM for it. Like the dumb sob I can be I didn't try starting the tuck before putting in the new PCM so I can not verify it started right before I put in the new PCM. Anyways once I dropped the new PCM in there it will crank but not start.
Then when I put the old PCM in it still showed the same symptoms. It originally seemed like a key immobilizer but my locksmith said the truck was not equipped with an immo he thought it had to be some mechanical reason but with as few miles as the truck has and the fact I know it started before I couldn't think what it could be.


I can verify fuel to the schrader valve on the fuel line but can not confirm to injectors. I also can't confirm spark but my engine has coil packs not wires so I'd assume that there shouldn't be any spark failure large enough to cause no start. My next best guess is maybe the crankshaft pos sensor let out on me for some reason?

I'm going to be doing some more poking around on it this weekend but thought I'd pick y'alls brains.
Thank you much, any input it welcome and appreciated.
 
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#3 ·
Could be the crankshaft position sensor, but usually it would throw a code. If you get a new one make sure to get the Mopar one, these trucks don't like other brands.

Maybe also a throttle position sensor or idle air control valve since when you would let off of the gas before it would die.


Start with the basics though, veryify its getting spark and fuel.
 
#4 · (Edited)
As stated I know it's getting fuel to the Schrader valve but have no way to check spark at this time. What I guess seeking most is what sort of programing is required to use a used PCM. After I tried with the old PCM again it threw p0601 yet again. I'm currently thinking that the old one is so fried it can't start the truck and that the new one has no way to start it if it's "locked out" w some sort of immo system.
 
#5 ·
Another symptom I'm having is the ABS light is flashing and binging. I found an ancient post saying that when the guy got a new PCM he had to get the dealership to sync the ABS system for it to work and he had the same symptoms I'm experiencing. Has anyone heard anything about this? I'm almost sure at this point it's an issue w computer coms.
 
#7 ·
I had some issues a couple years ago i think it may have been the PCM and when i switched out the PCM the abs light came on. the mobile tech that was helping me could not figure out why i told him forget it i need to get home from vegas. here is the strange thing i remember when i ordered the pcm from orileys the counter person asked if i had abs and i said NO because it did not have front sensors i then learned i do have it in the back with the sensor on the dif i wonder if a pcm is specific for abs not sure.
 
#8 ·
Hey all, first off hi I'm new to this forum and to owning a Dodge. There's quite a bit of backstory to my current situation but I'll try to make it brief.

Recently I acquired a 2002 Dodge Dakota RWD 4 door 4.7. It has only 45k miles on it and it had been sitting for a while. The original owner had it for a long while but never drove it when multiple years ago someone smashed his window while it was raining. After water got in the door panel the airbags went off. After that he let it sit for a while but it still started and ran but would die while driving.
Eventually he sold it to me for next to nothing because his mechanic told him it needed a PCM.

When I first acquired the vehicle it was throwing P0601 it idled fine, you could go into gears but would immediately die the second you let your foot off the gas if you tried driving.

So I bought a new PCM from a friend that was parting out the exact same truck. PCM numbers all matched.
Now the truck sat for about a month or two in between the time I got the truck to my place and bought a new PCM for it. Like the dumb sob I can be I didn't try starting the tuck before putting in the new PCM so I can not verify it started right before I put in the new PCM. Anyways once I dropped the new PCM in there it will crank but not start.
Then when I put the old PCM in it still showed the same symptoms. It originally seemed like a key immobilizer but my locksmith said the truck was not equipped with an immo he thought it had to be some mechanical reason but with as few miles as the truck has and the fact I know it started before I couldn't think what it could be.


I can verify fuel to the schrader valve on the fuel line but can not confirm to injectors. I also can't confirm spark but my engine has coil packs not wires so I'd assume that there shouldn't be any spark failure large enough to cause no start. My next best guess is maybe the crankshaft pos sensor let out on me for some reason?

I'm going to be doing some more poking around on it this weekend but thought I'd pick y'alls brains.
Thank you much, any input it welcome and appreciated.
did you have the pcm programmed with miles and vin??? i have bought a couple and it must be loaded with that information also depending on what year you have there is a theft safety in the ignition and both must talk to each other that means you new pcm might not be able to talk with the ignition i think the key has a chip in it.
 
#9 ·
Where to start, I tried disconnecting the battery and letting it sit, when I tried it again I got a high circuit for the fuel pump. Went ahead and checked PSI to valve... and nothing. So I put in a new fuel pump got great pressure to Schrader yet still no start. Then I was curious so I tried the live data mode on my OBD2 and it showed 0 spark ADV while cranking, I’m not positive but I’d reckon that means I simply don’t have spark.

Bruce to answer your question, yes I did program PCM for VIN.
Interesting about the ABS for the PCM. I am now thinking it is not immobilizer related as it still does not start with original PCM and furthermore even with the new one the security light does not blink which I’ve been told would happen if it was immo related. As well as the fact that these usually start for a second before having it kick in and shut it off. I have yet to try the new PCM with the new fuel pump so I suppose there’s still a chance that the old PCM is so fried it won’t start with it. My next step is to check continuity and voltage to all important relays and fuses. After I’ll attempt new PCM in hopes old one is so bad it won’t start. I am still not getting a no bus code. Hoping it’s a ASD relay gone bad or something. I will continue to update as I make progress and appreciate all input!
 
#11 ·
i forgot to ask.....are you getting spark? i had replaced my coil before i needed to and it works great....have you taken the distributor cap off to see that the rotor is turning when you crank it I have not heard of shafts breaking just thinking of anything. is the rotor on properly, did anybody change the wires to the plugs lately and put them on wrong, does the coil get 12vdc. you may have checked all of this i like to think about these things.
 
#12 ·
Not distributed I have individual coil packs. I took readings on voltage throughout fuse block. Found a few I was not getting 12v to. Then changed PCM and did it again. Same readings with new. With old PCM I’m getting P0601 with new PCM I am not getting any DTCs. Included is a picture highlighting the leads I am not getting 12v to I wonder if I have a breakage in wires somewhere or if it’s something else. I wouldn’t think it was a brake in wires as it started less than 4 months agoish. I looked at point of contact into fuse block and the wires seemed okay. Unfortunately I don’t have the capability at this time to check spark on each coil pack unless there’s a way to check via multimeter that I am unaware of. Tried replacing ASD relay to no avail. Also still NOT getting “no bus.” As well as I am pretty positive all grounds are good though I haven’t gone through each one. Though the biggest are getting volts through them.

On the 30Amp engine relay leads I am only getting 8mV which seems particularly concerning on the other two I’m getting ~6V. At this point I’m incredibly confused as to what it could be since I am getting fuel and the thing started strong so recently and has had nothing done to it other than it sitting. I legitimately don’t even know how to continue. I greatly appreciate the help.
 

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#15 ·
Fuel is brand new as I dropped tank and did the pump last night. Starter fluid makes no apparent difference, I think it must be no spark but can’t tell why it wouldn’t have spark. Grounds look ok but a little rusty on the actual bolts nothing I’d think would keep it from starting. And I’m getting 12v at all the grounds I tried.
 
#16 ·
In even more confusing news I went ahead and bought an in line spark tester and I am getting spark to both banks. I guess it’s the fuel injectors not firing or something? I tried jabbing my multimeter in the injector plug and cranking and it seems like it is getting electricity to the injectors. I mean... I don’t even know anymore maybe all 8 injectors are clogged from sitting a couple months but that doesn’t sound right.

Is it true that on live data if you are getting an RPM reading it means your crank sensor is good? I might just throw a crank sensor at it for sh*ts at this point.

Tomorrow I’m going to get a wire brush and some PB blaster and go ground to ground cleaning stuff up.
If that doesn’t do it I have no clue what will.

I am still also very confused as to why that one fuse lead has almost no power but yet it still has spark. Does anyone know what these fuses are for exactly?


Any help, even pot-shot ideas are beyond appreciated.
 
#18 ·
Crank sensor provided no change. At this time I know I have fuel to the injectors, I know I have spark at the plugs, I am not getting any codes, the only noticeable thing wrong with the vehicle is the lack of 12V at the highlighted fuse prongs.


If anyone knows what these wires are for or has a diagram tracing wires from the fuse block PLEASE let me know.

My only other thought is that somehow it jumped time, though it sounds fine when cranking. I may tear down the engine and check timing.

Edit:typo
 
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