Over drive switch problem

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May 4, 2020 | 02:53 PM

#16

Thaney423

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From: Tacoma Washington

Quote:

Originally Posted by Tom Pritt

can anybody tell me what is happening at the PCM by crossing these 2 pins on the OD button assembly? It’s what works to get the Trans back in OD After starting

May 4, 2020 | 02:54 PM

#17

Thaney423

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From: Tacoma Washington

Quote:

Originally Posted by Tom Pritt

can anybody tell me what is happening at the PCM by crossing these 2 pins on the OD button assembly? It’s what works to get the Trans back in OD After starting

I can't remember the pin out of the switch you'd have to chase wire color or test the pins to see what you have on each. If I remember right one should have 12v with the key on one should be 0v and one .2ish volts. Once you know that you'll know if your triggering the TC in the PCM or shorting it out so to speak. The way it works to my understanding and I could be wrong but pushing the switch sends a 12v pulse to the PCM which causes a change in shift strategy and switch's a ground for the TCIL circut causing the light to turn on.

May 4, 2020 | 03:14 PM

#18

Tom Pritt

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I do appreciate all the help from you guys. Glad I found this forum. Wish I would have found it a few years ago. Thanks for all the help. Was hoping it was something like a loose ground wire. But will keep checking. Like I said. Years ago it would jump in and out of OD like crazy. Then I got the idea to paper clip the button terminals and now that gets me into OD. Except when turning off the truck. That made me wonder about a ground problem as I can jump the bottom terminal in the housing and be good to go. Was hoping that would indicate the PCM was ok. Again. Thanks for all the suggestions. Tom

May 4, 2020 | 06:07 PM

#19

Mark Kovalsky

Frmr Ford Trans Engr

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From: SE Florida

The OD OFF switch is a normally open momentary contact device. When the PCM sees that contact has been made it will switch from OD ON to OD OFF, or if OD is already off it will switch to OD on. By jumping the two wires you are making the connection that the switch would normally make. There is no ground in this circuit. Each wire goes directly into the PCM. They are either shorted to ground or to each other somewhere between the PCM and the connections you're jumping.

May 4, 2020 | 06:24 PM

#20

Tom Pritt

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Where would you think a good place to start would be. Just curious. And thank you for the answer. I’ve replaced the shift handle and I believe it seemed ok once. Then went back to the problem. Also. The OD light will always come on prior to start. Jumping the terminals gets me into OD. If I push the button to take it out nothing will happen.ive dealt with this for over 4 years. When I asked a Trans shop about it they said I needed the Trans rebuilt and that 1996 was older than they normally work on. This was a factory ford stealership in south Fl. Thanks again

May 4, 2020 | 08:19 PM

#21

Tom Pritt

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Forgive me for my ignorance but if I’m able to cross the 2 pins and energize the OD solenoid. Where is the short ?? I’m thinking somehow there is another wire that may be shorted and not allowing current to pass through. The OD light will be on on the 1St start but go out after I remove the button and cross the 2 pins. Then I put the button back in the handle and the lights out. What is throwing me is I can push the button all day long and not get the OD light back on again ???? If I turn the key back off and on again the light will be on. Thanks again

May 4, 2020 | 08:26 PM

#22

Mark Kovalsky

Frmr Ford Trans Engr

Joined: Aug 1999

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From: SE Florida

Quote:

Originally Posted by Tom Pritt

Forgive me for my ignorance but if I’m able to cross the 2 pins and energize the OD solenoid.

There is no overdrive solenoid. You don't understand how this works.

Both wires go to the PCM. You are just completing a circuit that tells the PCM to turn on or turn off the overdrive function. What it is really doing is not commanding a 3-4 shift when it would normally be the right speed for a 3-4 shift.

Quote:

Originally Posted by Tom Pritt

Where is the short ?? I’m thinking somehow there is another wire that may be shorted and not allowing current to pass through.

Where is this imaginary wire? What does it do?

Quote:

Originally Posted by Tom Pritt

What is throwing me is I can push the button all day long and not get the OD light back on again ????

I'll bet with all of the making contact in the connection to the switch you've expanded the female pins so that they no longer make contact with the switch.

May 4, 2020 | 08:40 PM

#23

Tom Pritt

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Best thing I’m going to do is order another shift handle and button and reinstall as I’ve gotten pretty good at taking that deal apart. Will go from there and thanks again for the input. Tom