Tow/Haul mode

[Billett]

I've seen a few threads on the tow/haul mode of a truck pcm bring converted to a race style tune instead. When i asked my tuner about this he said that the factory computer cannot support that. Can anyone shed some light on this or should i be looking for a new tuner. This is the same guy who said that he could not change the output voltage on the tech signal, when I've been told that is also possible. These guys have a great record in the Corvette community but I'm starting to wonder if they are right for my build...

[Hart_Rod]

What ECM and transmission do you have? I know you can do that on a E38 ECM and the 6L series transmissions. On the older ECMs I think you have to incorporate the BCM to use the that function.

Edit: Just saw the 4L80 in your signature. You will probably have to incorporate a BCM to make it work. PM LS1Nova, I think he's done it.

Edit 2: When you say "tune", I think you are referring to making the shift points of the transmission "sharper".

[68GMCCustom]

I don't think it supports a completely different set of tune parameters...just changes transmission related like shift points, firmness, downshifts, etc.?

[Billett]

I realize it is just transmission related but tune is easier to type than transmission parameters. And yeah its an 03 engine and a 95 Trans.

[Big Port Jimmy 6]

Frost tuning was offering a dual flash PCM, push a button and a whole new tune. Jay

[Billett]

Don't really want a completely different tune. I mean it would be awesome, but I was really just looking for the tow/haul mode change. I was under the impression that it was possible with these models, but if it isn't at least I feel more comfortable with my tuner.

[BR3W CITY]

Its called "Performance Mode" in versions of HP tuners, and modifies shift points and tcc lockup changes and tq management (which you may need to re-edit because tq management does weird stuff)

There is an ecm pin where the tow button would wire in, which I think is pin 71 on the GenIII from going over threads.


As for on the newer stuff; its a bit harder to figure out. While there is still a tow haul mode, because of the BCM and TCM, what it does confuses me. There is still a modified shift table, but it also has stuff like engine braking, softened downshifts while loaded, and the Tu/Td functions seen on the Vette's.


oh and the tuner kinda sounds like a knobshine, but what do you mean by "Tech output"? Do you mean tach output, like for hooking up different tachometers? Its called tach output resolution, and yes, it can be changed (its not like changing a voltage number, but which mode/number of cylinders it uses as a tach reference). You can use a pullup in the circuit to get around this issue. Look at the LS2 w/ conventional Tach thread.

[Billett]

Yeah I did mean tach, typed it up on my phone so it must have "corrected" it. Tried the pull up mod with several different kinds of resistors and none worked. I went with the 680ohm suggested by lt1tech all the way up to the 10k ohm suggested by the guy I called at autometer, and everything in between. The only thing I can say is that I only tried 1/4 watt and not 1/2 watt resistors. Still, like you said also, it can be changed, but the tuner I talked to said it can't be...

As far as the performance mode, I know what it does at least in the early models, just wasn't sure if it was possible on my engine/trans combo or not because of what the tuner said. There isn't much information about it aside from pin 71 like you mentioned. In later model ecms I believe its a 50-something pin. What I have read a few places, and Hart Rod said, that a bcm is necessary for the tow/haul mode. I actually have a spare one, but that is a lot of wiring to do for just the tow/haul button. Can anyone shed light on that? All I see are a lot of posts on the ls1 forum about connecting pin 71, but nothing as far as a swap goes.

[Wasted Income]

All you need to do is have the "tow/haul" parameters enabled in the PCM. It's been awhile since I've been in one of those tunes, but there will be an drop down box for performance mode with 3 options I believe. "Off", "Class 2" (controlled by BCM), or switch. You just wire a switch in that grounds pin 71 on the blue C1 connector.

In the PCM, Performance mode = Tow / Haul. "Tow/Haul" has it's own shift speeds, shift times, shift pressures, kickdown, TCC apply, TCC release, and torque management calibrations.

[Wasted Income]

Originally Posted by VroomVroom68

Doesn't it just keep it from shifting it into OD?

I don't know how I could have made it any more clear...but here it is again...

Originally Posted by Wasted Income

"Tow/Haul" has it's own shift speeds, shift times, shift pressures, kickdown, TCC apply, TCC release, and torque management calibrations.

Did you get it that time?

Oh, and the trans will shift to OD in tow/haul.

[Billett]

Don't have any tuning software myself, but I'm assuming from the .hpt filetype that you're using HPtuners? I'm trying to find out what software they use, and why exactly they think this can't be done, just to clear my confusion about them.

Didn't know there were three settings! Thanks for the info. If they are using HPT I'll be sure to send them that pic and see what they say. They already unlocked the PCM for me and I'd like to stay with them for the tune, but I don't want to wonder about whether I could have had a better job done...

Br3w - thanks for the heads up on the tach resolution too. I knew you could change it but didn't realize it was only a cylinder/mode sort of thing. That changes things a bit. Guess I'll have to spring for the autometer box after all...

[Hart_Rod]

Originally Posted by Billett

Don't have any tuning software myself, but I'm assuming from the .hpt filetype that you're using HPtuners? I'm trying to find out what software they use, and why exactly they think this can't be done, just to clear my confusion about them.

Didn't know there were three settings! Thanks for the info. If they are using HPT I'll be sure to send them that pic and see what they say. They already unlocked the PCM for me and I'd like to stay with them for the tune, but I don't want to wonder about whether I could have had a better job done...

Br3w - thanks for the heads up on the tach resolution too. I knew you could change it but didn't realize it was only a cylinder/mode sort of thing. That changes things a bit. Guess I'll have to spring for the autometer box after all...

Here's a good thread on setting up the tach:

http://www.hptuners.com/forum/showth...ach-(autometer

[Billett]

Mystery solved. Tune shop thought I meant a full second tune as well, not just trans parameters. Guess I really need to be more careful about what I type. I really appreciate all the info on this though, because I really couldn't find as much as I was hoping for, and I like knowing how the ecm works even if I'm not tuning it myself.

[Billett]

I'll have to look through as I haven't seen that particular thread before, but I don't have high hopes. I've tried to get this damn thing to work through a lot of different ways...

[Hart_Rod]

Originally Posted by Billett

I'll have to look through as I haven't seen that particular thread before, but I don't have high hopes. I've tried to get this damn thing to work through a lot of different ways...

Will your tuner send you a copy of your tune? If so, you can email it to me and I can take a look. I did that setup (in the thread) yesterday on mine and it work perfectly.

[Billett]

Haven't asked, but I would hope so. It could come in handy diagnosing anything that might come up in the future. Didn't think to ask for it, but I definitely will.

[Hart_Rod]

Here's a write up on how to trigger the tow/haul mode:

http://www.hptuners.com/forum/showth...-Switch-Option

[VroomVroom68]

Doesn't it just keep it from shifting it into OD?

[BR3W CITY]

Originally Posted by VroomVroom68

Doesn't it just keep it from shifting it into OD?

In an obdI car, like a 94 Tahoe...then yes, pretty much. In reference to anything in the lsx subset...no.

Did you skip the first 3/4 of the page?

[Billett]

The guy's new here, cut him a little slack. but....

[Hart_Rod]

Tough crowd...lol!

[Wasted Income]

I hate spending the time to provide accurate and detailed info to only be questioned about it.

Aside from that...

[Wasted Income]

Billett, I know you got your issue taken care of, but this might help somebody else who searches for it.

I got back on my tuning laptop, and pulled up the section in EFI Live. I was wrong. There are 4 choices. There is a description of each in the screenshot below.

[ls1nova71]

I have a tow/haul switch in my truck, but to be honest I never use it. I just hooked it up since I was using the BCM for the other cool features, and it was just one wire and a switch.

[ls1nova71]

Wasted, any idea what the 'Manual mode' with 2 switches would do? Just wondering.