Just had my 518 rebuilt, put it back in and overdrive still dosen't work. Just looking for things to check before I let the tranny shop have it for a few days. Overdrive didnt work before but I knew it was smoked.

 

The easiest thing to do is to jump out the computer and put it on a toggle switch just to make sure that the computer is not the problem. If your able to turn the od on and off with the toggle switch then it has to do with the truck electronics that run it.

 

What is the easy way to jump around the computer

 

Tie into the wire's at the trans. 1 is blue the other is orange with a green tracer. I cut mine and ran the blue one to a "switched" hot and the other went to a toggle switch, out of the toggle switch I ran the other to chassis ground. What you are doing to complete the circuit is grounding it. You can cut the wires and test it that way but just make sure you leave enough so you can put the factory harness back together if the pcm is not the problem

 

or you can try to adjust the TPS. The TPS is what controls the overdrive engagement. Here is how to adjust it. If adjusting it does not take care of it then i would wire it to a switch. If it works with a switch then it is the TPS is bad and a potentiometer is your best option. Here is how to install a potentiometer. or you could just install a potentiometer if the TPS adjustment does not work because they are super handy to use to adjust your OD engagement point especially if you tow.

 

Zach is right. I forgot about that because my truck was never equipt with od. Try the tps first and go from there.

 

I checked the tps .65 at rest and 3.95 at wot

 

does the voltage go up nice and consistently when you are going to WOT?

 

https://www.dieseltruckresource.com/...highlight=code

Pay special attention to posts 2 & 7...

 

yes

 

I'd swap in a new O.D Selinoid regardless if I was rebuilding the trans. A trans guy wanted to rebuild my trans because the o.d was out. Quoted me 2k, well I ran without overdrive and the great guys on here led me to checking that and 50 bucks and some atf fixed the problem.. Try grounding in out manually, if that doesn't work, pull the pan and valvebody and replace the selionid and I bet you will be golden.

 

ive tried grounding out the override box tnen i grounded out pin 10 on the tcm with no luck to day ill try going directly off the sol. with a hot and switched ground if that dont work its going back to the tranny shop

 

got it fixed found broken wire down by the trans.

 

that would do it. Glad to hear that is working better for you!