New LS swap/install questions
 

Hello all,

I have a few questions regarding the swap.

1) When you start up the truck with the lsx motor is it normal that the idle is about 1000-1200 for a few seconds and then is slowly drops to about 600?

2) When I put the truck in reverse the engine revs up a little is this normal?

I just completed the 2-1/2" Stainless exhaust with flowmaster clones and really got to drive the truck for the first time rather than just starting it up and backing out or pulling it in the shop.

3) Does the truck computer need to learn to dial these issues in?

oh and

4) When I step on the brake and come to a stop it feels like the TC is still locked for just a second because the rpm drops to about 350 and than it releases and goes back to about 600?

2011 Chevy 1500 LTZ with 5.3 LC9- 6L80E

Thanks for the help !!!!

Re: New LS swap/install questions
 

I-2- and 3 sound like mine except it idles down to 703 RPM's!
I think they call it "Adaptive Learning"............. so drive it like you stole it.
As a side note I put 250 miles (freeway) on mine yesterday and got over 20 MPG!!

Re: New LS swap/install questions
 

Did you add a 4 prong brake light switch for the TCC torque converter lockup control?

Re: New LS swap/install questions
 

Yes I did the one that most have used here on the forum.

Re: New LS swap/install questions
 

That might not be right for a 2011, I believe they're the opposite of the older ones and you need power when the brakes are applied, not cut the power the way that the 4 prong switch does.

Re: New LS swap/install questions
 

I will have to look as I can't remember how i wired it. So you think the brake should supply power to the trans when the brake is applied? like the brake light switch?

Re: New LS swap/install questions
 

ls1nova71 is correct. The later e38 ECms want 12V with the brake applied.

Re: New LS swap/install questions
 

Well, you may still need the 4 prong switch. This may help you out. http://ls1tech.com/forums/conversion...ch-wiring.html

Re: New LS swap/install questions
 

Ok after reading your link to ls1tech (thank you). I think the problem is that I drove it with out the bed so no tail lights at all. So maybe it's not reading ground when the brakes are applied!! Or I am wrong? (((I am so confused))):)

Re: New LS swap/install questions
 

hi firstc10, I believe the problem is called "idle undershoot" caused by dirty throttle body, dirty Maf, and a fresh computer that hasn't learned idle speed yet. The old way was to drive above 45 mph, but if you are using drive by wire than I don't know for sure. Idle quality is helped by the use of the trans PRNDL switch, as the engine controller (ecm) prepares itself for the incoming load change. I mention these items as a help for others also, good luck, Brian culler

Re: New LS swap/install questions
 

thanks 68c10airstream
that is good information. all of it is!
I will be double checking my wiring tonight.

Re: New LS swap/install questions
 

The 6L80 has the PRNDL switch built in internally and provides that information to the TCM and the ECM via the CANBUS. The ECM will go into limp mode (I believe) if it was not getting the information from the TCM. As far as the IDLE and the shifting:

SHIFTING:

The 6L80 has adapative learning and it takes the transmission 20 or so shifts to "learn" the tune after each flash (regardless of whether the tune for the transmission was changed).

IDLE:

After a new flash, it takes a little while for the ECM to learn the tune, but I think part of your problem might be that the tune that you have doesn't have the correct tire size and gear ratio. This will throw all of the transmission shift calculations off.

TCC:

The E38/T43 (ECM/TCM = GEN IV) require a TCC signal that is opposite of the GEN III setup, i.e. power to the TCC with the brake pedal is pushed. Both the GEN III and GEN IV setups require special wiring if you are running LED tail lights. Check out this thread:

http://67-72chevytrucks.com/vboard/s...d.php?t=604032

Re: New LS swap/install questions
 

I seem to post this alot lately;

if you have any tcc issues AND you have an aftermarket cam, make sure tune has bee setup to ignore some level of false knock, and adjust the misfire counter. A big cam throws sensors out-of-phase and causes intermittent lockup issues.

Re: New LS swap/install questions
 

After looking into my wiring diagram I infact have it wire like the Gen III. I will rewire it tonight.
I believe most of my problems I asked about were probably caused by the wiring issue with the Brake switch.

Rob my ECM was programmed for the tire size and gear of the rearend. well atleast I gave this info to LT1swap.com when I sent him the ECM to program.
Oh and my motor is bone stock.

Also I know you all have wired a relay in and a resister but can you just wire to the light switch to the brake lights? or do you need that wire to ground when the brake is NOT applied? other than through the brake light bulbs to ground?

Re: New LS swap/install questions
 

Good point Brew. Poly-urethane motor mounts will also add to the false indications.

If you don't have LED tail lights you will probably be OK. Try it first and see if it changes anything. If not, you will probably want to add the resistor. If you have your tune, email it to me (robhartley@aol.com) and I can check the tire/gear size.

Re: New LS swap/install questions
 

First C10,

I have the exact same set-up but my engine is LMG and does the exact same thing. I thought it was normal but now you have me second guessing myself!

Re: New LS swap/install questions
 

I am only running the brake wire on a 4 pin relay, I am going to switch to a 5 pin this weekend like HartRod has and see what that does.

Re: New LS swap/install questions
 

Ok so I couldn't stand it and had to know. So I took a longer lunch. (Don't tell anyone). I just added the blue/white wire from the TCM to the white brake light wire on my switch the orange is 12+ power from the fuse block. And started it up. Shifted gears while in the shop, forward and reverse and felt really good. I haven't drove it yet but already sounds and feels better.

Re: New LS swap/install questions
 

Did it rev high for the few seconds like before??

Re: New LS swap/install questions
 

Only when I started it up. But I think that is from me disconnecting the battery while it's in my shop. So I left the battery connected thought maybe that it made the computer at funny with the power off. Will check on that tonight. When I put it in gear from park it didn't rev like before.

Re: New LS swap/install questions
 

Ok so I drove the truck tonight and it seem to do ok but still feels like the TC is still locked up as the engine almost dies when I slow down pretty fast and come to a stop. If I slow down normally like coming to a stop sign I don't notice it.

Ok so during one of my start ups I got an engine code P0171 and P0172 lean banks 1 and 2

Is this normal since the computer is learning. Ok I also took a few pictures of the obdII display. Hope someone can decode all this stuff.

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