ECU questions

[Bret B]

Done a little searching through this section of the forum and learned there is more to an LS swap than I originally expected. I am kicking around a couple decisions. First would be a connect and cruise complete package. Second would be rebuild anything I find from a donor and piecing it all together. With that, I believe my question applies to either option.

A comment was made by a friend of mine, the ECU will control the transmission so there will be no need for two control boxes (one for engine and one for trans). I find that in the connect and cruise packages, a standalone transmission brain box is required. I may ask this wrong, but after talking with Pace Performance and a couple local "experts", they say a separate standalone transmission controller is required for all "E" transmissions and the GM ECU's will control the engine only. When looking at a complete used drop out from a Camaro or trucks, they don't have a standalone box connected to the trans harness, only 1 box, the ECU. I'm expecting to use a 4L65E trans if I go the drop out direction.

So, the direct questions is, do I have to use a standalone transmission brain box or is there an aftermarket ECU which does control the engine and transmission? Really hope I'm asking the right question.

[ls1nova71]

Well, your sort of right, but I can tell you are new to this stuff and it can get kind of overwhelming sometimes. You're kind of getting into semantics though. The connect and Cruise package is an LS3, which is a GenIV engine, so it will need a TCM (transmission Control Module) to run the transmission. This engine uses what GM calls an ECM (Engine Control Module) to run the engine. The older GenIII engines used a PCM (Powertrain Control Module) which controls both the engine and transmission, hence the term 'powertrain' rather than just 'engine'. Your local experts probably meant that some kind of controller is required for all E transmissions, but not all are separate, some of the earlier Gen IV's have the transmission controller actually mounted inside the trans so it appears there is no controller, but there is. Hope this helps and didn't just make things even more complicated!

[Bret B]

Yes, I will firmly admit to being new to LS stuff. Not the first go around with engine swaps, but with computer controlled, oh yeah, color me green. I still need to research the electrical harnesses and all the joy that comes with that.

So I'm assuming not all GenIII were a PCM (both controlled) do to different transmissions, or is that inherent for all the GenIII? Does this mean there are no aftermarket PCM's (controls both) for GenIV applications? Example using an LS3 (L99) and a 4L65E, and only one PCM to control both. Another example (I know it isn't GenIV), an updated LQ9 with 4L65E and one PCM to control both.

[1971Stepside]

Bret, I'm right here with you brother. So many wires LOL

[Haggar]

Hmm, I have two LS setups..

First is up and running/driving well, Thats a 1971 Jimmy, I have an Gen III LQ4 and 4L65e, both are run from the single ECU, a '0411' Red/Blue ECU.

The second is a stroked LS2 Gen IV motor, from a trailblazer SS. This is going into my 67 Plymouth Valiant.. probably with a 4L880e. That one I have a stock E67 ECU, that controls the transmission also (can do 4L60s, 80s, and 6L80s with it). So it's possible.

[Clyde65]

I thought 6l80s had the TCM in the trans?!

[BR3W CITY]

They do.

[Haggar]

Oops, yes, correct.. They have a TCU inside. Although they don't work as standalone, as far as I know, and need an appropriate Engine controller to keep them happy.

Anyway, for a 4L65e, yes, you can control that from a single controller.

Buying used vs new is a tough decision. I'm 1 for 2 on mine..

My LS2 ended up having 2 rod bearings on their way out, and a few other issues. I wish I had bought a crate LS3, which is what I had wanted, but decided to 'save' money.

My LQ4 was the opposite. I just wanted a stock engine, so I got a long block from a recycler.. when I got it home, I found that it had CNC ported heads, a Lunati cam, dual springs, aftermarket retainers, pushrods, ARP bolts everywhere, etc.

[davepl]

If you can swing the budget you sound like a "Connect and Cruise" kind of guy. And that's not because the alternative is hard or more work, it's just the unknowns.

When you get an engine and trans and computers as a system and you install them everything "just works". But when you combine a crate LS and a takeout trans and an aftermarket computer, now you've got a challenge.

I'm a computer programmer so I even bought the wrong model (auto vs manual) to get the $500 rebate and then reprogrammed it to be the kind I needed. You don't want to do that kind of stuff I'm sure, so get a package!

If you can't afford Connect and Cruise, just invest in patience. In my case I did the LS3 crate engine and not the full package, but even so the engine and its computer were a matched set from GM.

[Clyde65]

If you have any ( or can make one) friends in the car dealer business, you can go to an auction and buy a wreck or? After looking them over real good.

You can also do an online auction by just registering and setting a $ amount.

[nsb29]

How ever you obtain it if you do not go with connect and cruise by complete drop out that way you have the correct combination of engine transmission ECM And gas pedal my brother bought his motor and transmission separately and had His share of problems and he knows what he’s doing

[Bret B]

Continuing to look into this. There are a lot of options, more than expected, and more ways to get to the same result. Bottom line is, do research, make a plan, get the parts needed, and stick to the plan.

[davepl]

A drop-out or take-out isn't bad IF a few things are true:

- You get the WHOLE thing you need or a professionally cut down harness.
- You know how to cut down a harness and eliminate the many circuits you don't want and need
- You know how to adjust the computer to adjust and compensate for the circuits you removed

Legalities aside, you don't want to drive it around with a constant MIL condition either.

You can't just yank an LS2 out of a GTO and bolt it to the trans mount and duct-tape the ECM to the shroud. Well, you could, but...

[Bret B]

davepl - if I go with used, my intent is to get a complete drop-out (focusing on engine, trans, ECU). If that doesn't happen, then I have to plan for additional TCU, or that is what I'm understanding. Harness will likely be aftermarket with the elimination process already done, since I already will be replacing the chassis harness at the same time. As for computer, I have a connection to get the ECU initially worked to get the security and such removed. After that, it would need additional/optimal tuning.

And true, with enough duct tape, lockwire and chewing gum, one could do unimaginable things....

[nsb29]

LMAO whether you buy a drop out or a connect and Cruise you will have issues like Engine and transmission mounts exhaust that you have to work out you can have your ECM Tuned I used a company called current performance your wiring harness can be sent out to be redone or you can buy a standalone harness it is not rocket science good luck with your project