PCM wiring

-

mychristine

Active Member
Joined
Nov 27, 2014
Messages
33
Reaction score
23
Location
Nj
i have put a 2013 5.7 in a 68 Barracuda. I have it all wired and attempted to fire it up for the first time today. The harness is from swap specialties....and before I even go farther, please do not buy anything from this company....please tell all your friends not to buy anything from this company. They are helpful until they get your $- then they are literally gone. The harness was just thrown in a box with zero instructions. So....the engine will crank, but it is using the old harness for cranking only (no connections from ignition switch to pcm, or pcm to starter at all). When the key is on, I get power to the coils, but the power cuts off during cranking. I get no power to the fuel pump (key on or cranking), (no issues with pump itself- I can jump it and it works fine). My question is what tells the PCM to switch on and power what it needs to during cranking? I’m missing some link between the old harness and the new harness and again, get zero support from that awful company. Thank you in advance for your help!! I uploaded a couple pics of the car...looking great, getting close!

2F683057-B25B-4E7F-90B9-DE75CFDC6B34.jpeg


379B1120-6009-4F9D-85F1-DC6795D96868.jpeg


7FD81EC5-7CEA-4C81-A2C3-836C5D1BB1D6.jpeg
 
First, nice car. Second, I ran into a similar issue with both my Cuda (FAST) and Challenger (Holley) and in my cases it had to with where my switch was connected in the system. I cannot remember specifically what the issue was but it has to do with supplying power from the switch to the PCM and coils when cranking. I know this is not overly helpful but will the car start if you try remotely (assuming you are using a Mopar starter relay)?
 
Thank you! When you mean switch, you mean the ignition switch? I’m assuming the PCM needs to be powered during run and start....so I jumped the pcm directly and it still does not start, nor does the pump get powered. I feel like there should be something connected to “start / wake up” the PCM when the engine starts to crank. But like I said, I have no connections between the PCM and the starter circuit at all. Should there be, I seem to find answers both ways when I look it up....but no clear instructions how to connect it to try? Thanks again....any help would be much appreciated!!
 
I'm not familiar with that harness but does it come with a relay and wiring to power the fuel pump?
I would just double check the relay wiring, make sure it is getting a good 12v source, verify the trigger wire is energizing the relay coil - report back what you find.

As for your coils and cranking... The mopar ignition switch gives power to ignition and cranking on two different positions. So I think your problem may be that the "run" wire drops voltage when the "start" wire energizes - try adding a jumper between the start and run wires coming from the ignition switch - this should feel power to the "run" wire even when cranking -

basically our PCM is not getting power during the cranking cycle and therefor wont light the engine off.
 
Thank you! I’ll look for the cranking power source and hook that up, as well. The weird thing is that I already jumped the PCM directly from a constant 12v source and it still didn’t power the pump (I’ll check the coil when I do that again). Yes, it does have a pump relay and it is wired directly to the pump. Maybe that relay is just bad? I’ll check some things tomorrow and report back- thanks for your input though...I really appreciate it.
 
Oh, one last thing (for now)....the pump is not activated even on the “on” key position. It’s not just when it is “cranking”. It’s almost like the PCM is just not “waking up”?
 
Could of told you that about Swap Specialties. I provided by 6.1 engine in my Duster as well as a stock harness and PCM years ago, never heard back from there any they left me high and dry. There from a few hours north of me, but I can't have any issues with law enforcement and I know they'd call if I showed up.

Riddler
 
Yes, it’s by far the worst company I have ever dealt with...it took me months to get my harness after harassing them, and then months more to get my pedal and sensor package. They literally will not speak to you as soon as you give them money. I had to threaten them to get my stuff, I still cannot get a response from them for support- pathetic. They deserve to go out of business.
 
Well first, part (or even all) of your problem might be right in the car---nothing at all to do with the "new" harness

Here is how Mopar ignition switches work.

You have main battery in, and outputs are:

"ignition run" (ign1) which powers the underhood "stuff" like ignition, alternator field, and VR but is hot ONLY IN RUN. This wire goes DEAD during 'start'

"bypass" or (ign2). This is the normall brown wire that goes from ign2 at the igntion switch to the coil+ side of the ballast in stock harnesses. This is hot in 'start' and bypasses the coil relay AND IS THE ONLY SOURCE of ignition power during 'start.'

"accessory"---hot in both "run" and "acc" positions of the ignition switch, also goes cold during 'start'

"start"....normally yellow, feeds out into the bay and keys on the start relay

NOTE: The 'start' yellow wire and the bypass 'ign2' are both hot at the same time but ARE DIFFERENT CONTACTS in the switch to avoid backfeed issues
 
Thank you so much....that gives me more clarity. Thanks for all the feedback from everyone gives me a few things to try tomorrow....in fact, I’d try them now if my wife wouldn’t kill me (it’s midnight).
 
Welcome.........I forgot to mention that in systems where there is no longer a ballast, such as MSD or HEI ignition conversions, you need to jumper IG1 to IGN2 and use that one wire to feed the igntion.

IF YOU ARE still using an ignition with a ballast, this becomes a bit more complicated in the case of an EFI because it must be powered during cranking, and the original circuit can cause backfeed problems.
 
No, I’m not using the ballast....just power directly to the PCM. So....the ignition 1 wire (blue) has 12v when the key is on and drops to 0 when cranking (as it should). However, the ignition 2 wire (brown) has 0 with the key on, and just gets a quick burst of about 4 volts when it starts cranking- then goes back to 0 as it is cranking? I’m assuming this is not correct?

However, it still doesn’t make sense to me (even if I used those wires to power) because I can jump the PCM with direct power and I get power to the coils, but no spark and no power to the fuel pump?

Thanks again....its been very helpful as I dig in deeper!
 
What are you using for a pcm and are you sure the security has been disabled on it if it is a factory one?
 
What are you using for a pcm and are you sure the security has been disabled on it if it is a factory one?
I’m not sure of anything since it came from swap specialties (absolutely awful experience and no support). What I do know is that it is a used stock ecm from a 2008 - 2010. My engine is a 2014- that can also be a problem...but I guess I’ll get to that. How would I know if the security was disabled?
 
No, I’m not using the ballast....just power directly to the PCM. So....the ignition 1 wire (blue) has 12v when the key is on and drops to 0 when cranking (as it should). However, the ignition 2 wire (brown) has 0 with the key on, and just gets a quick burst of about 4 volts when it starts cranking- then goes back to 0 as it is cranking? I’m assuming this is not correct?

However, it still doesn’t make sense to me (even if I used those wires to power) because I can jump the PCM with direct power and I get power to the coils, but no spark and no power to the fuel pump?

Thanks again....its been very helpful as I dig in deeper!

The IGN2 should be hot with full battery voltage whenever the key is in "start." Backtrack through the bulkhead connector and see if that is the problem. If not it is right at the key. That wire only goes one place......from the ignition switch, through the bulkhead connector, to the coil+ side of the ballast. Might be the ignition switch connector as well
 
Also if you have not already, I would take that ign1/ ign2 splice and use it to key a relay, then use the relay to feed the underhood loads, ign, efi, alternator field, etc.
 
Also if you have not already, I would take that ign1/ ign2 splice and use it to key a relay, then use the relay to feed the underhood loads, ign, efi, alternator field, etc.
Thanks, again. I did trace it back right to the ignition switch and tested the voltage right at the switch- it’s the same. I guess it must be my ignition switch then?

But regarding the pump and the coils, they still do not get power even when I power the ecm directly...so there is still some other issue. I’m starting to wonder if it is my crankshaft pos sensor. Since this setup is actually from a 2010, the sensor is different. I’m wondering if the pcm triggers those relays when it sees movement?
 
Without original OEM diagrams, no idea, and the OEM diagrams are actually a real PITA to deal with.
 
Update....so, I reached out to Swap Specialties and Andy responded. He thinks there is a SKIM issue, or the ecm is just bad. I sent it back to him....fingers crossed that I get it back quickly!!!
 
Update....so, I reached out to Swap Specialties and Andy responded. He thinks there is a SKIM issue, or the ecm is just bad. I sent it back to him....fingers crossed that I get it back quickly!!!

Update on this. I sent the ecm back on feb 26 when I wrote the last post. That fu*@ing piece of sH*# disappeared completely and I still never got my ecm back! Please, whatever you do...do not give your business to swap specialties. The guy is an absolute piece of sh*&!! As far as what I have done...I bought a new ecm with the same part number and sent i5 out for the skim delete. I just got it back today, hooked it all up- I get fuel pressure, I get power to the injectors and coils, but no spark. My understanding is that the ecm controls the grounds and that’s what pulses the injectors and coils. I changed my crankshaft sensor and my cam sensor is new. Does anyone else know what triggers the ecm to start pulsing the ground that I should be looking at? Also, does the ecm itself need to be grounded....it is bolted underneath the dash, but I’m not sure how good of a ground it is...although I didn’t think it needed to be? Any thoughts would be greatly appreciated!
 
I am not familiar with the new hemi, yet. But the crankshaft postition sensor and the camshaft position sensor are what tells the pcm to fire the coils and injectors. If the crank and cam position sensors for different model years of engine are different, which they very well could be, the pcm likely will not fire them. It’s worth your time to match the year pcm with the same year engine. On the coils, you should have power, ground, and signal. On the injectors it’s just power and signal. The signal you can test with a oscilloscope or a noid light. Hope that helps. Now I’ll go look up swap Specialties.
 
From their “downloads” section. Do you have the main power connect 8 gauge wire powering your fuse box? That’s what powers their whole harness
5ABB081A-0D43-4F1E-B464-A94F9DE42BA0.png
3341AFFE-0505-4E97-A600-9FB9859BBD08.png
 
Also look at the last note on that page.
The “heavy” pink wire note. Those have to be tied in to your ignition
 
7402A028-B224-43B3-B7EC-150164EB0570.png
I blew it up a little more so you can read the whole note
 
View attachment 1715542981 I blew it up a little more so you can read the whole note
TT5- thanks so much! I really appreciate your help and quick responses. So, the swap specialties harness came with ZERO instructions....just a bunch of wires thrown in a box. I’ve looked everywhere on that site for instructions because the POS won’t respond once he takes your money. I just went into the downloads section and there are instructions for everything, except for a Hemi? Can you send me a link to that because I can’t read it all from the images. Thanks again!
 
-
Back
Top