Tow/Haul - performance button question

[ZJM861]

i have an 04 silverado motor with an 02 intake and computer... 4l60 in my 87 and heres what i was wondering:
is there a way to tell the computer (by pressing a button wired in somehow) that the tow/haul button is pressed? this is in my 87 silverado, not the correct 99+ truck... ive read the thread about ls1 computers but not a truck computer. if i remember, the bcm recieves the command and im sure the signal goes through the bus- or + wires.. im sure someone here has figured out its possible or not.
thanks

[1badc10]

doesn't that funtion run through a stock truck's BCM? Not sure... would have to check schematics.

[oscareltemblo]

I believe you can but you have to turn it on, on the computer by going to trans then general and pick class 2 in hp tuners and load it to your tune then find the schematics for your pcm pins one of those should activate it I believe not sure though.

[ZJM861]

bump for a 2 year old thread.... anyone figure this out?

[ZJM861]

another question, after viewing some info on alldata, it seems that you might have to program this module if you replace it... would a junkyard one need to be programmed? im not a gm tech, but i use to work at a chevy dealer so maybe the same electrician tech still works there and remembers me.. if so I might have to leave work and talk to him in person with a case of beer in one hand and a note pad in the other. From the transmission schematic, it looks as if the tow haul is just a momentary contact between ground and a pin on the bcm, and then the bcm makes its signal to the PCM. sounds easy enough but I swear I read someone had tried to wire the BCM up like I just described and it didnt work. Any GM electirican tech here that can chime in on the programming of the BCM.
If anyone has any BMW questions, Im your man GM BCM's not so much..
thanks guys

[wheelerman420]

pin 71 or something like that on the blue connector on the 0411 pcms. then u got to get a momentary switch to use to trigger this to a grnd i believe. Then change settings in hptuners to one switch.

[ZJM861]

pin 71 or something like that on the blue connector on the 0411 pcms. then u got to get a momentary switch to use to trigger this to a grnd i believe. Then change settings in hptuners to one switch.

pin 71 shoes not used... i know the ls1 computers can wire in a momentary ground switch but thats as far as i got besides the bcm theory lol

[Frost]

pin 71 shoes not used... i know the ls1 computers can wire in a momentary ground switch but thats as far as i got besides the bcm theory lol

duh, your F-body didn't COME with tow haul either

That was the right advice that he gave you (all of it was correct).. Alternately, you may have done a search for tow haul : http://www.hptuners.com/forum/showth...light=tow+haul

[ZJM861]

duh, your F-body didn't COME with tow haul either

That was the right advice that he gave you (all of it was correct).. Alternately, you may have done a search for tow haul : http://www.hptuners.com/forum/showth...light=tow+haul

thread got off track on that one.. ive got the 0411pcm which is facotry 02 silverado PCM. he mentioned a pin number and my pcm, and thought he might have mixed up my question with a f-body PCM solution.

Ive got all the diagrams on the BCM as alldata offers and put together a schematic that might work... only thing is im not sure if the module can program running only these wires.. it should but Im no GM tech. Also another member shared some info on what hes learned.. see post
http://67-72chevytrucks.com/vboard/s...3&postcount=11

"I tried for 2 months. What i learned is flashing the anti-theft out of the PCM makes the PCM ignore what input it gets from the BCM. Maybe you can use a PCM that doesnt have the anti-theft removed the have the anti-theft/passlock turned off in the BCM? The PCM & BCM will need the same VIN flashed into them."

the anti-thieft is in the pcm to begin with right? the BCM doesnt have that stuff in there or does it? Can HPTuners do anything to a BCM?

heres the schematic I merged together...

[Chris@HPTuners]

generally the PCM only controls the fuel enable for the engine. The BCM controls the starter relay, the door locks, the key remote, etc.

Depending on what type of VATS system you have it is either looking for a sqaure wave input or a serial message password from the BCM.

As for the Tow/Haul/Performance Mode switch it can be either hardwired or via a serial message from the BCM. The Performance Mode Option setting decides which it is. If your BCM was never set by GM to send a serial message then it can't be changed. BCM cannot be reprogrammed.

[ZJM861]

Is there a way to see (by part number on the BCM) what type of signal the module would send... but as long as the truck had a tow/haul button the BCM should have that signal.. right?
As HPtuners and the BCM goes, can HPtuners tune anything to the BCM? Just incase disabeling the VATS in hptuners effects the function of the class2 singals from the BCM.
Is there a way to tell what type of VATS say my PCM has using HPtuners?
Thanks for the replies!

[Frost]

thread got off track on that one.. ive got the 0411pcm which is facotry 02 silverado PCM. he mentioned a pin number and my pcm, and thought he might have mixed up my question with a f-body PCM solution.

Ive got all the diagrams on the BCM as alldata offers and put together a schematic that might work... only thing is im not sure if the module can program running only these wires.. it should but Im no GM tech. Also another member shared some info on what hes learned.. see post
http://67-72chevytrucks.com/vboard/s...3&postcount=11

"I tried for 2 months. What i learned is flashing the anti-theft out of the PCM makes the PCM ignore what input it gets from the BCM. Maybe you can use a PCM that doesnt have the anti-theft removed the have the anti-theft/passlock turned off in the BCM? The PCM & BCM will need the same VIN flashed into them."

the anti-thieft is in the pcm to begin with right? the BCM doesnt have that stuff in there or does it? Can HPTuners do anything to a BCM?

heres the schematic I merged together...

The 411 PCM isn't just a Silverado PCM; it's in Vettes, F-bodies, and more. I don't understand what you are after, I thought it was tow haul, but the solution to that is here. Am I misunderstanding?

[ZJM861]

oo, I did not know they used the same part number on the computers... In that case, I wonder if I would be able to perform the same modification the the pcm pin 71 as the LS1 PCM's. How does the pcm know what pin 71 does... what i mean is in the diagrams I have access to shows pin 71 for truck and ls1 PCM's to be "not used". I do not want to damage my pcm but I was wondering how the it was figured out pin 71 was the one to use a momentary ground on.
Thanks!

[Frost]

you have to set it in the calibration as noted by wheelerman above.

[ZJM861]

thanks Frost, I will take a gander at the transmission settings and see if there is a setting for the class2... if not I will go to the repository and look at an LS1 cars PCM. That would be wicked cool if the trucks PCM worked the same way
thanks

[Frost]

What? They are the same PCM. The posts say one switch, not class 2. What is it about your setup that you seem to think everyone is wrong? <-- Internet is hard to read intent; not being ugly just don't understand what you are after.

[ZJM861]

Thank you for your help Frost! My intent wasnt to say everyones wrong, but
As far as the PCM goes, again, I just didnt know they were the same thats all. From what I read, it think I just misunder stood what I was reading... I could have sworn that I read that gen III trucks couldnt get the option to work like the LS1. I tried looking back to find where I misunder stood it, but I couldnt find it..
Thanks again Frost for helping me understand... if you live around Houston, I'll buy you a drink

I'll do this modification this weekend.
Referencing this post
http://www.hptuners.com/forum/showpo...30&postcount=7
I wonder if the trucks PCM has this same wire to use for the LED as pictured.. otherwise the same author made a neat circuit board to display tow/haul mode

[Frost]

You have options.... though I am almost certain there won't be any issue making it work, you always have the option of using an F-body OS where it's tried and true since this is a swap. I use it for cars with larger than 200-hits that need different shift strategies as the bottle goes up.

That link you posted, I seem to recall that was for the LT1 cars, not the 411 PCM.

[ZJM861]

yup, I just checked out the alldata schematic and was going to edit my last post and delete that, but you already replied... man your fast!

[ivanls1]

What? They are the same PCM. The posts say one switch, not class 2. What is it about your setup that you seem to think everyone is wrong? <-- Internet is hard to read intent; not being ugly just don't understand what you are after.

so this is the way too tune for da towhaul mode ??? im a newbie sorry for da question lol just want to get it right