My cummins is throwing this engine code at me. I cant shift in overdrive? Is this an EC problem?

 

P0753 - Trans 3–4 Shift Sol/Trans Relay Circuits

I swapped out the transmission relay under the hood and the problem is still there. Won't shift into overdrive, starts out in wrong gear when accelerating from a stop. I have to manually shift 1-3 to get going.

I have drive 120 miles tomarrow, I hoping this can be fixed quick! TIA.

 

You may want to replace your governor pressure solenoid and sensor under the tranny pan. You'll have to drop the pan, drain fluid and replace both units but it's doable albeit messy.

 

I am now wondering if this could be a wiring harness issue. I've lost more than just Overdrive, even though the only code I get is for the 3-4 Shift Solenoid.

I've also noticed that the tranny heats up while stopped at a light for a while (in gear), which leads me to believe that the lockup isn't slipping properly. Also when I accelerate from a stop it just sits there and slips in 3rd gear. I have to manually shift down to 1st to get it to go, but it doens't quite make it all the way to 1st, it starts out in 2nd instead.

So I either have major electronic issues, or a harness came undone. Does anybody have a link to a diagram for the harnesses and solenoids?

Thanks for your help guys!

 

FYI -

I decided to tear into the transmission that week and see what I could find. I tested the solenoids ( Overdrive solenoid and Governer Solenoid ) and came to the conclusion that they were bad.

I ordered both from the dealership, which cost me about $250 for everything. The Overdrive solenoid comes with a new harness and everything. I put the new parts in, put the tranny back together (misc valve body parts & pan) and now it works as good as new.

Just figured I would give you guys a closing to this problem.

 

I was just about to post that when all of my governors and sensors died on my tranny, it did the same thing yours did. Glad to hear you got it fixed.

 

Glad to hear you got it fixed and glad you posted it. Now anyone that wants to read about this problem will know how to fix it themselves. Man I love this web site! This site saves me big $$$.