posted my problem a couple of time and even email dave goerend and a couple of other tranny guys about my problem and nobody has heard of it. my truck goes into tow haul mode by itself. the button lights up on the dash and its in tow haul. it may go in and stay until i hit the button or the light may flash several times . the problem is getting worse it may go into tow haul mode by itself several time on my 16 mile commute to work. i disconnected the button sat hoping it was the button. its not. with button disconnected the truck goes into tow haul mode and stays. i ran a jumper wire from the ground-no change in symptoms, i befriended a dodge diesel tech who is going to look at my truck on thurs but he has already told me the chances are its the torque converter. i have also recently replace the governor solenoid and transducer. somebody educate me- tranny shifts fine, fluid changed at normal intervals. i assumed my problem was electrical- could it be the torque converter?? (sorry so long)

 

Are you loosing OD when the light comes on?

The TH switch on your truck is only OD lockoput nothing more. If the light is coming on and your not loosing OD its likely a cluster problem. If your loosing OD when the light comes on then something in the harnes sis scuffed and causing the ECU to think the button has been pushed.

The button just notifies the ECU to drop OD which is completely electrical and under control of the ECU.

 

tow haul is functioning properly. its just doing it on its own. when the light comes on i lose od. i tried to trace/follow the wires but i lose them under the dash. i did not think it was/is a bad torque converter.

 

I don't think the TC has anything to do with it . It sounds as though you have a wire rubbing and causing the switch to engage. it could even be in the trans itself. The overdrive solenoid itself.

 

my truck is a 2005 and may have a different auto trans setup all together,
It is my understanding that when i push the t/h button, it does not lock out the overdrive mode, just change shift settings.

that fuction may be different in your 2004.5 model.

if yours is like mine and when the t/h light comes on, then if o/d is unlocking you may have different or more problems.

hope its just an electrical issue.

 

i thought it was electrical myself. like i stated i tried to trace the wires-but lost them up in the dash. if i knew where or how they connected at the other end ( i guess into a plug at the ecm?) i would just run new wires from the switch to the the other end to see if that solved my problem.- (eliminated the existing wires).

whiskers -good suggestion on the overdrive solenoid- i wonder if there is a test,etc to determine if that is malfunctioning.

 

Check for codes. If you don't have any doubtful on the OD solenoid. They are on or off and there is not a lot to them malfunctioning. If it was bad you could turn OD on and off all day with no difference. There is no feedback loop for performance, only for resistance and thta will generate codes.

Not positive but I think the OD switch function signal is put on the bus from the cluster and encompassed in a data stream. That may be for the CAN systems though and not your truck. You would need the FSM and the ECU pinout to see if that signal wire is there but it may be a sense wire from the cluster that gets activated by the momemtary switch in the stalk. Just depends on how they implement it.

Try unplugging and resetting the big harness connector on the firewall . Sometimes they get a little corrosion and resetting them cures these glitches.

 

Good news, its a direct sense wire from the pictures in the FSM. You might try clipping this wire and see if the jumping in an out quits. That will tell you if its in the harness to the switch or the switch itslef.

Its pin 13 on the C2 connector:

 

no codes. thanks no_6_oh_no for the diagram/info- that helps alot.

 

no_6_oh_no found the wire on the ecm c2. going to be a little more involved than i thought- in order to cut the wire to run a jumper. i first have to get enough slack out of the harness and wire bundle,etc to do that. for the hell of it- i put a test light on the dark green (tow/haul overdrive sense wire) at the plug on the harness side- i got nothing. so this is not a power wire? the tow haul switch has no dedicated fuse. so a "sense" wire just picks up a reading from the ecm, correct?

 

The TH button is momentary switch so it just flashes a power signal when deporessed to tell the ECU to turn OD on or off. Normally there would be no signal on it and I think the signal has to drop to activate the OD off. If you power it constantly nothing may happen.

Need to cut it and see if that stops the OD Off from getting turned on randomly. That will tell you if there is a short in the wiring harness of the ECU has issues.

 

you are correct if you power it constantly- it stops working ( i tried that to see what would happen) may be this weekend before i have a decent amount of time to get into this with a jumper wire. doesnt unhooking the plug accomplish the same thing as cutting the wire to see if it stops the random o.d. off? when i unhook the plug truck will go into tow haul mode and just stay in tow haul- it will not randomly shift in and out. the diesel tech is suppose to look at my truck on thurs or fri (will find out for sure tomorrow) so may be i will get lucky and wont have to start peeling back the ecm harness and cut!


whats your thoughts of running constant power to the switch to make it stop temporarily? truck is almost undriveable with how many times it goes into and out of tow haul mode. would i damage the ecm or anything by doing this?

 

Depends on what your unhooking and if the ECU needs to see resistance on that circuit. From your description unhooking the plug cause no OD and that means the ECU is monitoring that circuit.

What you can do is wire a switch in to keep it OD so you can drive it. Find pin #6 I believe on the trans harness connection, the round one, and scotchlock a wire to it. Run the wire to SPST switch in the cab. Wire the other side of the circuit thru a 33 ohm 1/2 watt resistor then to a good ground. When you engage the switch it bypasses the ECU and engages OD. Won't drop out no matter what the ECU does.

 

The tow haul button sends a ground pulse to the ECM to request tow mode,
Does the truck stay in tow mode when it does it on it own ?

 

truck does not stay in tow haul mode when it does it by its self. the tow haul light will flicker on and off and you can feel the o.d. engage and disengage. sometimes its so bad i have to manually hold in the tow haul button so i can get down the road. dodge mechanic now has my truck. he is driving it to work this morning so we shall see-later in the day i imagine.