Hello I have a problem with getting my Tow/Haul mode to work. I can't get the tow/haul to engage at all. The trans shifts correctly and the TQ locks up correctly but Tow/Haul will no engage. It stopped working suddenly one day and have tried for three months to fix it with no luck. I have replaced all the electrics in the trans and the front control module after being told it was one thing after the next. Checked all the wiring and nothing wrong. Checked the Tow/Haul switch and have voltage when you push it and then none when you let go so a signal to activate it. I am at a lose with what the problem and need help.

 

check the wire from the switch to the trans. it supplies ground to the tranny. check for open to ground thru switch. one wire is ground the other goes to solenoid in tranny. also check for a broken wire in the steering column. you might try a alternate ground, to see if the solenoid works. Good Luck ;;;;

 

this should be the wire schematic;;
http://www.dodge.com/bodybuilder/200...trolsystem.pdf
8w31-3-/-14

 

What do you mean it doesn't work? The trans shifting algorithm or the light on the dash?

FYI, the TH on an 05 is NOT an OD off button like earlier trucks if your thinking thats what the problem is.

TH on your truck will make the trans **** later and firmer plus a more aggressive lockup sequence.

 

What I mean is that the light is not coming on and the trans is not shifting any difftent. It use to go into tow haul and shift like u say later and firmer on the shifts when it worked. Started up the truck on day and no light for tow/haul and no change in the shifts. I know it dose not lock out over drive. The trans shifts normal ( for a throughout all the gears and locks up th TQ ) but when you push the tow/ haul button now nothing happens. No light and no change in shifts or lock up like it use to do. Like I said I have tried and replaced everything electrical with no luck. Hope some can get me pointed in the right direction. Thank you.

 

Here is th epin out for the ECU conector and the TH sense wire. This says OD Off but I think its the same wire.

Check it and make sure it is sending the signal to the ECU when you hit the button.

If it is showing a signal its probably the ECU, either bad or lost the programming for it. If not you have a bad connection between the button and the ECU.

 

OK I can not figure this out. I still can not get tow/haul to work. I checked the wires and no breaks. I then checked everything in the trans and the front control module. I have 3.51 volts at the switch and then when you press the switch it goes to 0 volts. You let go of the switch back to 3.51 volts. I also have the same voltage at the ecm 3.51 then 0 then 3.51. I am being told It should be 5 volts and that is the problem now. I am unsure if that is true and also if it is where is the voltage coming from. I then can see where I would be loosing 1.5 volts. I could use some more help and advise because I am at a loose. Other then the tow/haul not working every thing ells works fine. Shifts fine and locks up fine and now other electrical problems at all. Thanks

 

Here is the test sequences from the FSM. Could be the switch is bad or worse, the PCM.

P0751-O/D SWITCH PRESSED (LO) MORE THAN 5 MINUTES (CONTINUED)
2. CHECK THE TOW/HAUL OVERDRIVE OFF SWITCH
Reconnect the Tow/Haul Overdrive Off switch harness connector.
Measure the resistance between ground and the O/D Tow/Haul Switch
Sense circuit in the PCM C3 harness connector.
Press the Tow/Haul Overdrive Off switch button.
Does the resistance change from above 5.0 ohms to below 5.0
ohms while pressing the Tow/Haul Overdrive Off switch button?
Yes >> Using the schematics as a guide, check the Powertrain
Control Module (PCM) pins, terminals, and connectors for
corrosion, damage, or terminal push out. Pay particular
attention to all power and ground circuits. If no problems
are found, replace and program the PCM per the Service
Information. (Refer to 8 - ELECTRICAL/ELECTRONIC
CONTROL MODULES/POWERTRAIN CONTROL MODULE
- REMOVAL)
Perform RE TRANSMISSION VERIFICATION TEST VER -
1 (GAS). (Refer to 21 - TRANSMISSION/TRANSAXLE/
AUTOMATIC - 48RE - STANDARD PROCEDURE)
No >> Replace the Tow/Haul Overdrive Off switch per the Service Information. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - 48RE/OVERDRIVE SWITCH - REMOVAL)
Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (GAS). (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - 48RE - STANDARD PROCEDURE)

 

OK Thank You I am a little confused but will try it and let you know. I have no trouble codes set and if it was a PCM would I not have some other problems. I (Knock on wood) do not have any thing other then the Tow/Haul not working. Is it even possible to loose the programing.

 

Might not have a code if the ECU is bad. Things just don't work right. If the power is being supplied by the ECU and is supposed to be 5 volts and is only 3.5 that could very well be the issue. Tough to tell on the ECU sense and control circuits as a lot of that is not specced in the FSM. Seems the default fix if the switch checks out and there is not broken wire is replace the ECU.

 

Dose anyone have both the wiring diagrams for the two plugs that go into the ECM. I am trying to figure out me problem and would like to know what wire/number on the plug goes where. Thanks

 

The picture I posted is the C2 connector and has all the pin outs. Do you need the C1 connector for some reason?

 

The one you posted is cut off at pin# 25 and I am assuming that it is the front one of the two connectors on the ECM. The reason I ask is their is no wire in pin # 13.

 

Crap! Your right. Let me get the rest of it. The C2 connector is the rear most of the 2.

 

Thank you for help. I am praying it is not the ECM. Thanks again