So another thread got me thinking about my options. I live in California so emissions are a fact of life.

I need to do a more thorough look through it the existing wiring diagrams but I'm pretty sure I can combine both a 2003 and a 2005 harness that would allow me to simply switch PCMs when needed. The combined harness would have all the connects necessary for each PCM. As long as you never plug both in at the same time... I can see it working. That way when it comes time for smog I just unplug the 05 PCM and plug in the 03 PCM/TCM
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The 03 TCM plug and the 05 plug that plugs into the TCM part of the 05 PCM aren't the same. Doing the swap directly usually entails repinning the trans harness so it can plug into the newer PCM. Also the 2003 only has one cat with two O2 sensors; 05 uses two cats and four O2 sensors. If you have SKIM this will be a huge problem even before that.

 

I believe I've done a poor job explaining my idea, apologies.

If I'm sitting here with both a 2003 and a 2005 harness, I see no practical reason why I can't splice the two together in such a way as to provide me with two branches, one that feeds into a 2003 PCM/TCM and a 2005 PCM. Never would both the 2003 and 2005 PCM be plugged in at the same time, less magic smoke is released. The additional o2 sensors for the 05 PCM would be installed and ran directly into the branch for the 05 harness.

Lets take connector C4 for example. In the swap you normally take '03 TCM pin 60 and move it to '05 C4 pin 1, this is the OD solenoid control.

Instead of moving a pin, you splice so the OD solenoid control wire gets sent to both the existing '03 TCM connector and the '05 C4 connector.

I'm aware of the SKIM issue. I would just have to be mindful to unplug the module before plugging in the 05 PCM.

Imagine on smog day you just need to unplug one PCM and plug in another into its own connector branch and away you go.

 

That sounds like entirely too much work a plus leaving way too many openings for electrical issues down the road. Not only that, you'd be switching between two different systems that operate at different fuel pressures (2003 48 psi, 2004+ 58 psi); I imagine the 05 PCM would be cranky unless you changed your fuel pump but then the 03 PCM would be with all this extra fuel. Also you might fail smog because of your exhaust; you'd have to pick one of two different setups. If you keep the 03 setup for smog that will be codes in the 05 PCM and possibly rough running. I don't know if they do visual inspection but if you use the 05 cat setup that means the PCM would only be reading one bank of cylinders; it may or may not deal with that successfully.
If I recall my CARB reading correctly (if things haven't changed and/or gotten worse), you can legally install a newer engine so long as the emissions controls are in place and not polluting more. You could install the full 05 conversion (which would require the extra O2 sensors, EGR & a 04+ spec fuel pump) and your truck should pass emissions for a vehicle 2 years newer. Would just require a special inspection, yes?

 

It's just about impossible to source the entire exhaust system, that would be easy. The junkyards cut out the cats, wont even sell them to you anyways.

 

https://www.rockauto.com/en/catalog/...converter,5808
https://www.rockauto.com/en/catalog/...stem+kit,10727

 

I found those before, but I don't believe they're 4x4 compatible.

 

Luckily it doesn't matter what you believe LOL. It would be idiotic on Dodge's part (from a cost perspective) to have a different exhaust setup for each unless the platform absolutely mandated it (like the LX platform). As per 2005 parts book, same pipe/cat combo for all. I've highlighted the 5.7 one. 3.7 & 4.7 use a different one unto themselves as does the SRT-10.

 

oh I see the crossover is farther in the back not by the front driveshaft. I need to make a phone call to the referee..

 

Looks like I can't avoid the EGR issue.. My head appears prepped for it, but the hole that runs into the exhaust port isn't fully machined out. So I can either put a new head on, or try finish machining it on the truck (drill one hole, drill another hole and tap). If it fails I end up putting a head on it anyways.