TOOSLO5

Is the tow/haul mode available on a 4L80 application? Only thing I seem to come up with as a tow/haul search is stuff that looks like it pertains to the 60's. The engine/trans are out of an 06' express van and I would like to try to wire the tow/haul if available on this is possible. In the threads I found wire #71 is mentioned. In the blue PCM connector there is no wire #71 and in the green there is a serial data wire so I am a little lost here.

Thanks!

76LQ9TA

iTrader: (1)

It's on my 06 2500HD silverado w/ LQ4 and 4L80E

TOOSLO5

Anyone got any idea what wire on the 80 application needs the momentary ground?

76LQ9TA

iTrader: (1)

The tow/haul switch grounds c1 59 on the pcm. It is wired through the bcm.

12secSS

iTrader: (30)

Tow/Haul mode is a extra function of the ECM, it has nothing to do with the transmission. The ECM tells the Automatic Trans when to shift, to what gear, and what pressures to use ... the trans could careless if it is Tow/Haul or Normal or Cruise or Hot. That is inthe ECM's code.

TOOSLO5

Thanks for the drawing! I saw 59 on the pinout I have but assumed it was for data transfer. Now that I have the complete drawing I will try it out.

Thanks again for the help!

TOOSLO5

Checked terminal 59 on the blue PCM connector and the terminal is empty. The engine/trans/harness/pcm all came out of an express van. Can I use the empty terminal to enable tow/haul?

G-Body

iTrader: (4)

Who reprogrammed your PCM? and what year PCM is it? My guess is that you would have to use blue pin 71, my 2001 PCM also has the same schematic as above where the class II serial data from the BCM enters at pin 59, but since I am not using the BCM I use blue pin 71 to control the tow/haul. Jesse at wait4me set my PCM up and I think that it said right in EFI Live 7 that I needed to use blue71. I had to add a wire in to do that.

TOOSLO5

There are no wires on 59 or on 71 on the blue connector. The PCM is the factory 06' unit. The engine/trans/harness/pcm were a complete pull out from a van. Since everything is from a van I would not think a reprogram would be required to enable this function but maybe I am wrong. A connector pinout I have shows class II serial data on on this pin but there is no wire. Could it be that the 3/4 ton van on up does not have a tow/haul button on the dash as my wifes 1/2 ton van does?

TOOSLO5

Anyone got any ideas on putting a wire on 59 and 71 and trying them out? It looks to me like I should try pin 59 first rather than 71 since this is where wire from the BCM would go to the PCM from the factory. I dont see how it could hurt anything and if the tow/haul featoure is not part of this PCM's tune from the factory. Nothing should happen when the momentary ground is applied if thats the case.

Gbody-did you use a factory type female pin to go in your PCM plug where you added the wire? If so was that something you got from the dealer. If not what did you end up using.

Thanks!

trackbird

iTrader: (4)

I'm not sure that you'll actually want/need tow/haul mode in a car (I'm assuming this is going into the Chevelle in your sig?). It just (mostly) holds shifts at part throttle (in case you lifted while pulling something heavy, it saves hunting in and out of gear). I know it does other things, but my truck says I can tow without using it (so there is enough line pressure), it seems to just change the shift patterns in the transmission logic (from the ECM). I've played with it in my 2007 C3500 when I'm not pulling and I don't think I'd ever use it in a car application. Maybe I'm wrong, but that's been my experience with it.

G-Body

iTrader: (4)

I used a factory pin. I just went to the junkyard and searched through the cars until I found a PCM connector with the same pins. Other people have used a pin from the emissions stuff and just switched its location in the PCM connector.

trackbird: I don`t know if this is the same way as the tow-haul mode is setup from the factory, but when I put it in tow-haul the part throttle shifts are delayed, I am locked out of overdrive until 50mph so theres less stress on the trans, and the torque management is put back in. (For normal driving the torque management is deleted)

It depends on what you are planning on doing with the car. I use my car to tow stuff once in a while, and for the bigger stiff it is nice to have. If I am towing a small utility trailer I don`t bother putting it in tow-haul mode,but it is nice to have when you put a 3000lb boat on the hitch, or flat tow a suburban

TOOSLO5

G body-Thanks for the info. I am going to try hooking it up, dont know which wire I will use yet, and see what happens.

Trackbird-car is not tuned other than a base engine tune Speed inc threw in it for me to get the car running. The car is very very driveable even without a full tune. The only issue is the trans tune. If it were not for the exhaust note and tach you wouldnt even know the trans had shifted. I want to hook up tow/haul to see what happens and if the shift firmness and shift points work for the application. If they do I can carry over some of the tow/haul trans tune to the daily driver tune. If the tow/haul shift points and firmness are too harsh I can tune somewhere between the two.