2004/2005 Electronics Swap

[Lochabar]

Hey, guys!

Been reading on the boards here for a while now, but I haven't come across the answer to my latest question: how is compatibility for electronics from the '04 to '05 LS and vice versa?

Long story short, I'm Frankensteining my old '05 LS and my new (ironically older) '04 so I can put away some money and do a little more reading before I get into reading down the heads (external coolant leak on one of the gaskets and compression loss in cylinder 6). So the bulk of my question is: I would like to keep my recently cut keys and my FOB, so I know that I need to swap the PCM, theft module, and cluster at a minimum - but is there anything else I have to move over for the car to run right? Maybe the BCM? Both are 3.9s, I've pulled the full option code lists, and I don't see anything that's too different between them (cosmetics mainly, and the new one doesn't have back-up alarms).

Any advice you guys would be greatly appreciated, and thanks for all the helpful stuff you guys have posted on the past!

 

[joegr]

It will work, but it's going further than you have to.
The "theft module" is in the instrument cluster, so that would have to be swapped.

You could just swap the lock cylinders and program the 04 to accept the keys from the 05. If you have two working keys with the 04, then you don't need anything else to do this. If you don't, then some scan tools can do the programming. I think that Forscan is probably the cheapest one that apparently can. Still, this seems like a lot of trouble to avoid buying a $30 key or two.

The fobs are related to the driver's door module. There's no need to swap it. There's a simple programming procedure in the owner's manual. It just involves turning the key off and on the right number of times and hitting buttons on the remotes.

Head / head-gasket failure is extremely rare on the 3.9. Failure of plastic cooling system components that give symptoms very similar to head-gasket failure is very common.

 

[SeaPro]

My last coolant issue gave every indication of a blown gasket except for coolant in the oil. I knew it was unlikely, however decided to test the compression to make sure. Luckily my compression was good, lowest 155 and highest 165. What did you get for compression on your bad cylinder? 10% variance is ok IIRC.

I'm also doing a complete swap between an 03 V8 and 05 V6. The V8 is rusty, the V6 is lacking in performance. From what I've been able to determine, you hit the nail on the head with the PCM, Cluster and Ignition.

 

[Lochabar]

It will work, but it's going further than you have to.
The "theft module" is in the instrument cluster, so that would have to be swapped.

You could just swap the lock cylinders and program the 04 to accept the keys from the 05. If you have two working keys with the 04, then you don't need anything else to do this. If you don't, then some scan tools can do the programming. I think that Forscan is probably the cheapest one that apparently can. Still, this seems like a lot of trouble to avoid buying a $30 key or two.

The fobs are related to the driver's door module. There's no need to swap it. There's a simple programming procedure in the owner's manual. It just involves turning the key off and on the right number of times and hitting buttons on the remotes.

Head / head-gasket failure is extremely rare on the 3.9. Failure of plastic cooling system components that give symptoms very similar to head-gasket failure is very common.

I'm going to swap the interiors, anyway, because the one is best to hell, so it seems like I might as well move over the modules while I'm at it. As far as the head gasket, I've read that they're extremely rare, but I got under her and I could see a mist of coolant spraying out of the base of the head, under the manifold. But I do plan on reworking the cooling system, because the last thing I need is for it to blow up after all of this work. Pulled the interior of the donor today, and got it pretty much all done in about four hours.

 

[Lochabar]

My last coolant issue gave every indication of a blown gasket except for coolant in the oil. I knew it was unlikely, however decided to test the compression to make sure. Luckily my compression was good, lowest 155 and highest 165. What did you get for compression on your bad cylinder? 10% variance is ok IIRC.

I'm also doing a complete swap between an 03 V8 and 05 V6. The V8 is rusty, the V6 is lacking in performance. From what I've been able to determine, you hit the nail on the head with the PCM, Cluster and Ignition.

When I checked the compression, 6 blew like 120, so I'm thinking either a valve or the rings, but it might be the gasket, too. I figure I'll just garage the motor and rebuild it when I get the time. Hopefully tomorrow I can blow through the rest of the surgery and get her up and running.