Hello, i’m currently in the process of doing a 3.9 to 5.9 swap on an 03 dakota sxt, it is pretty basic but i’ve ran into a couple problems. My truck that is getting the 5.9 is california emissions, now my parts car is a 03 durango rt federal emissions. My question is, if i have the federal emissions wiring harness, Ecu, and exhaust (1 cat vs the 3 on cali) even tho i’d rather run no cats, this should work right? I live in new york so i’m not worried about getting caught or anything stupid like that. Only reason i ask is because dick head at advance auto won’t sell me federal emissions y pipe with cat on it, he says he’ll get fined and that a federal emissions cat will blow up my 5.9? LOL part store workers man

 

you will have po420 p0430 codes setting due to no cats. nothing will blow up! go to another store and buy whatever exhaust you want.

You: I need a federal emission y pipe for a 03 dakota
jobber: sold

 

But if i use the federal emissions y pipe with the cat i shouldn’t have any codes right? haha i’m gunna go to napa and see what they have

 

if have the fed wiring harness, fed pcm..and there is a cat and the pcm is only looking for 1 post cat 02 sensor you should be good.

 

Okay that’s what i thought i’m just double checking with you guys, thanks very much

 

You can fool it however you'd like. My method was to remove the 2 mini-cats, leave the third main cat, then use O2 extensions to relocate the two downstream sensors behind the main cat.

 

That’s not a bad idea if i were to have a california wiring harness, but wouldn’t that also run a code? I feel like the littlest change on those things would **** everything up

 

My truck is a california truck, but I took the pre-cats out so functionally it's a federal truck, but electrically it's still Cali. No codes - Since the downstreams still sense a "cleaned" signal from the main cat, they are happy.

Since you're switching the engine harness instead of just adding injectors 7 and 8 to the V6 harness (what I did, staying with Cali PCM), since the PCM and harness will both be federal, then you should just need to put the O2's in their appropriate place, before/after the main cat.

If you want an extra play...you can just swap the Y pipe from your donor truck, unless you had to cut it out? Exhaust manifolds and pipes are in the same place on V8 and V6.