Bare minimum for pcm to run engine

The SRT-4 Board is for general questions regarding the factory turbocharged Neon, the SRT-4. Rumors, hints, tips-and-tricks, and all general maintenance and repair questions belong in this forum, as well as beginning modification queries.
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chris97sohc
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Bare minimum for pcm to run engine

Post by chris97sohc » Sun Nov 01, 2020 4:27 pm

I'm trying to figure out what the bare minimum requirements are for the stock PCM to run the engine without interface with the dash and cluster.
belalegosi wrote:why not just keep the cat?

:dunno:
We like to contribute to global warming, one neon at a time.

occasional demons
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Re: Bare minimum for pcm to run engine

Post by occasional demons » Mon Nov 02, 2020 6:12 am

Being in the SRT-4 section, assuming this is an '03 to '05, I have heard that the car will not run without the cluster. You could possibly get the SKIM disabled, and it might run without the cluster, because I think that would be the only reason, if this is true, that it would not function, as I believe the cluster is tied into the SKIM module.


Hopefully someone with more knowledge can confirm if this is fact.

The cluster also communicates various info like fuel level to the PCM, basically so it won't trigger a misfire code when the fuel is below ~1/8 tank or so. But in a boosted car, you don't really want to risk running lean enough due to low fuel, to misfire anyways. I'm not sure what changes they may have made for the low fuel signal in an SRT PCM. I would think there would be added protections for warranty reasons alone. Granted a warranty is no longer an issue, but it was when the car was made.

Worst case, is you take the cluster board out of the cluster body, set up a resistor to the fuel input telling the cluster that it has over 1/4 tank, and it should be happy. This will take up less space, but not really less wiring. You could probably get rid of all the turn signal/high beam indicator stuff. The PCI bus and "fuel tank resistor" would have too stay. The PCI bus will take care of the SKIM communications and gauge communications. I don't know if not having gauge motors will have any impact.

I think any basic cluster would work, if you are going to try this. No need to destroy an SRT cluster.
- Bill

desmodromic wrote:You have to remember what's important here, while they make New humans everyday, they'll never make another Neon.
Skellibert wrote: Fri Oct 13, 2017 3:42 amThis is a daily by the way, not a track car or fun buggy.

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chris97sohc
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Re: Bare minimum for pcm to run engine

Post by chris97sohc » Mon Nov 02, 2020 8:49 am

You may or may not have seen my rear wheel drive SRT4 project thread on this forum. That car will be running full interior so it won't be an issue. But I'm also starting another rear wheel drive SRT4 project in a different platform vehicle and was hoping to figure out a way to run dual factory computers. The factory computer for the car that the SRT4 is going into so it can control and communicate with the body control module and additionally the SRT PCM to only control the engine function while still tying in some of the SRT4 PCMS outputs into the swapped cars harness such as OBD2 information. It may not be possible but I figured I'd look into it before going stand alone engine management.
belalegosi wrote:why not just keep the cat?

:dunno:
We like to contribute to global warming, one neon at a time.

occasional demons
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Re: Bare minimum for pcm to run engine

Post by occasional demons » Mon Nov 02, 2020 10:13 am

chris97sohc wrote: Mon Nov 02, 2020 8:49 am so it can control and communicate with the body control module and additionally the SRT PCM to only control the engine function while still tying in some of the SRT4 PCMS outputs into the swapped cars harness such as OBD2 information.
Not sure what it is going into, but neons didn't have a BCM, so not sure what would happen there if it seen one via PCI bus, because that's how they would communicate. Probably nothing, or very little, as there wouldn't be much need for BCM inputs to the PCM.

The closest thing to a BCM in a neon would be the RKE module.

I had toyed with the idea of using a 300M climate control panel in my 2gn, but I would have also needed the BCM module too make that work. Since I didn't have access to an complete 300M for the needed parts, or wiring schematics, it never got too far.

Plus the digital HVAC controller was known to fail, so that was the nail in the coffin.
- Bill

desmodromic wrote:You have to remember what's important here, while they make New humans everyday, they'll never make another Neon.
Skellibert wrote: Fri Oct 13, 2017 3:42 amThis is a daily by the way, not a track car or fun buggy.

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chris97sohc
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Re: Bare minimum for pcm to run engine

Post by chris97sohc » Mon Nov 09, 2020 9:53 am

So I know the pcm needs to communicate with the cluster and skim module to run the engine. Trying to find a way around that. Basically in theory if I wanted to start and run the engine on a stand with no interface with anything but the pcm, that's what I want to accomplish for the simplicity of a swap I have in mind.
belalegosi wrote:why not just keep the cat?

:dunno:
We like to contribute to global warming, one neon at a time.

occasional demons
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Posts: 11290
Joined: Fri Apr 13, 2007 10:34 am
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Re: Bare minimum for pcm to run engine

Post by occasional demons » Mon Nov 09, 2020 11:51 am

Well the SKIM can be turned off, but you'll need the equipment to do it, or see if PCM Plus or maybe Kevin Sykes still does this?

I am not sure on how the cluster functions to make it run, and I have only read that it needs to be there. I can't recall if I tried running my 2001 without the cluster, but even if it did, the SBEC PCM is a different platform. But like I mentioned earlier, the necessity of the cluster might very well be tied to an active SKIM. I will almost bet, if you can get the SKIM shut off, you won't need the cluster.

The one edge an SRT PCM has, is it can be more easily tweaked than the regular neon unit.

So it is probably more of an issue of finding someone knowledgeable enough, than it is actually making it run as a stand alone.

Unfortunately knowledge is getting somewhat harder to find, as people have moved on.
- Bill

desmodromic wrote:You have to remember what's important here, while they make New humans everyday, they'll never make another Neon.
Skellibert wrote: Fri Oct 13, 2017 3:42 amThis is a daily by the way, not a track car or fun buggy.

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chris97sohc
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Re: Bare minimum for pcm to run engine

Post by chris97sohc » Mon Nov 09, 2020 12:55 pm

Yeah no kidding I'm feeling pretty alone these days. Admittedly though I've mostly moved on from the platform and only really deal with the engines these days. Front wheel drive just doesn't do it for me anymore
belalegosi wrote:why not just keep the cat?

:dunno:
We like to contribute to global warming, one neon at a time.

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