Tow haul indication

[tjm]

Does anyone know how to use an MM3 tuner to determine whether your in tow haul mode or not? I've monitored engine RPM and transmission gear with constant pressure applied to the throttle to see if the transmission shifts at a different point. So far I cant tell the difference between tow haul on/off. I do have Robs tunes and am running the 30HP MPG tune so the tow haul switch disables OD and I did add the switch to the ECM to ground pin 39 on the connector closest to the firewall.

Any pointers would be appreciated.

 

[AH64ID]

I am pretty sure that you either have tow/haul or OD off, but not both on that year.

 

[tjm]

I am pretty sure that you either have tow/haul or OD off, but not both on that year.

Stock Yes. But with Rob's Tunes from MM3 tuning - the stock tow haul button is converted to OD on/Off.

From Rob
The custom tuning on your truck has changed your Tow Haul button into an “overdrive
off” button. Your new custom shift schedule combined with OD Off is a very capable
configuration, but there is a way to have it all... In the interest of providing customers
with every option possible, these instructions enable you to access the tow haul shift
schedule should you desire (it has slightly elevated shift points). This will require
installing a switch that gives owners of 2004-2005 trucks the same options as
2006-2007 trucks have: Regular shifting, Tow Haul Mode, and OD Off Mode.
In order to access tow haul mode, you will need a pigtail: cummins part# 3164263
(shown below). This item sells for about $10 and will provide the connection to your
ECM at pin 39 of the rear (C2) ecm connector. To install, you need to pull the red
spacer out of position 39 with tweezers and slide the metal tube of the pigtail in until it
clicks. Then you need to run a wire from the crimp/heat shrink section into the cab to a
switch which you provide and can install wherever is convenient. The other pole of the
switch goes to ground, so when the switch is “on”, ecm pin 39 connects to ground. This
tells the ECM you are requesting the Tow-Haul shift schedule.

I'm trying to figure out - what are the elevated shift points. watching Speed, engine RPM, and gear indicator I cant tell the difference.

so with tow haul enabled do you shift at +250 RPM?, 400 RPM? vs when its disabled? Does anyone know the stock tow haul shift points?

I cant seem to find it

 

[AH64ID]

Gotcha, I missed the pin 39 when reading the first time.

I would talk to Rob then. You cannot use the tuner, AFIK, to know if you are in TH or not. The difference in shifting will be based on how he programmed it, so that's why I would ask him.

 

[tjm]

Gotcha, I missed the pin 39 when reading the first time.

I would talk to Rob then. You cannot use the tuner, AFIK, to know if you are in TH or not. The difference in shifting will be based on how he programmed it, so that's why I would ask him.

Will do. There is no PID for TH mode on or off. that would be nice.