TC locked in forward, OK in reverse, just changed solenoid pack - PowerStrokeNation : Ford Powerstroke Diesel Forum
 
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post #1 of 9 (permalink) Old 11-18-2009, 03:20 AM Thread Starter
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TC locked in forward, OK in reverse, just changed solenoid pack

Well, I have a big problem!! Originally the O/D light flashed, and the TC briefly locked up, even when trying to stop the truck, the light stopped flashing, and the TC unlocked. It threw up a P0743 code.

So then a few days later the TC completely locked up, I was able to drive it a mile or two (in very heavy traffic) with the tranny still shifting, but with the TC completely locked, I had to knock it into neutral when I came to a halt.

Had it towed home.

I changed out the solenoid pack for a new pack. It works OK in reverse, but when trying to go into forward the TC is locked up. I had assumed that the P0743 code being an electrical failure, that changing the solenoid would fix the problem.

Could this be an electrical problem, that allows it to work in reverse, and not forward? Or is the TC (and probably the tranny) toast? I would assume that the TC being locked in frwd and not reverse is an electrical signal to the solenoid, does that make sense?

Can I send a signal to the TC to manually unlock it?

Thanks in advance for any help!!
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post #2 of 9 (permalink) Old 11-18-2009, 09:58 AM
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Re: TC locked in forward, OK in reverse, just changed solenoid pack

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Originally Posted by triumph406 View Post
I had assumed that the P0743 code being an electrical failure, that changing the solenoid would fix the problem.
Bad assumption. It most likely is a short in the wiring harness.

The PCM grounds the solenoid to lock it. You probably have that wire shorted to ground. There is a hydraulic signal that forces the converter clutch to unlock in reverse even if the solenoid is on, so that's why you don't have the problem in reverse. I don't have a wiring diagram to be able to tell you which wire.
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post #3 of 9 (permalink) Old 11-18-2009, 10:23 AM
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Re: TC locked in forward, OK in reverse, just changed solenoid pack

Ford dealer in IL had called to tell me that my tranny was shot. I told him to unlock the TC switch and then try it out. lol It was doing the same thing you are seeing.

Is this truck new to you? Is it equipped with a manual TC lock switch?

If not, it sounds like a short in the harness as stated above. If you just purchased the truck, look for a TC lock switch, or possibly wiring for one that was not removed porperly and is grounding out.

The purple/yellow wire is the one for the TC lock BTW.

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post #4 of 9 (permalink) Old 11-19-2009, 01:28 AM Thread Starter
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Re: TC locked in forward, OK in reverse, just changed solenoid pack

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Originally Posted by moore20017.3 View Post
Ford dealer in IL had called to tell me that my tranny was shot. I told him to unlock the TC switch and then try it out. lol It was doing the same thing you are seeing.

Is this truck new to you? Is it equipped with a manual TC lock switch?

If not, it sounds like a short in the harness as stated above. If you just purchased the truck, look for a TC lock switch, or possibly wiring for one that was not removed porperly and is grounding out.

The purple/yellow wire is the one for the TC lock BTW.
The truck is new to me.

I talked to the previous owner, and apparently he bought the truck cheap with the TC locked up, and that was an electrical problem. It does have a TC lock switch that was disabled when he put a new computer in. I think your right, it does sound like a wiring problem. The TC lock switch is next to the boost gage on the pillar gages. I will have to pull the pillar gages off and start tracing the wiring.

I talked to somebody who suggested pulling the connector off the tranny, and seeing if the TC would lock when going into forward, if it didn't, then it would probably be electrical, if it did it would probably mechanical.

Thanks for the help!!
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post #5 of 9 (permalink) Old 11-19-2009, 01:35 AM Thread Starter
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Re: TC locked in forward, OK in reverse, just changed solenoid pack

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Originally Posted by Mark Kovalsky View Post
Bad assumption. It most likely is a short in the wiring harness. .
Your right, that was a bad ($300) assumption. I really should have spent more time trouble shooting.

Quote:
Originally Posted by Mark Kovalsky View Post
the PCM grounds the solenoid to lock it. You probably have that wire shorted to ground. There is a hydraulic signal that forces the converter clutch to unlock in reverse even if the solenoid is on, so that's why you don't have the problem in reverse. I don't have a wiring diagram to be able to tell you which wire.
What happens if I interrupt the yellow/purple wire that goes down to the connector? Will this stop the TC locking up? Will this damage the computer?

Thanks for the help!!
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post #6 of 9 (permalink) Old 11-19-2009, 10:24 AM
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Re: TC locked in forward, OK in reverse, just changed solenoid pack

That will unlock the converter if it is an electrical problem. It won't damage anything, but it should make the OD light flash because the computer can sense that the circuit is open.
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post #7 of 9 (permalink) Old 11-19-2009, 04:05 PM Thread Starter
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Re: TC locked in forward, OK in reverse, just changed solenoid pack

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Originally Posted by Mark Kovalsky View Post
That will unlock the converter if it is an electrical problem. It won't damage anything, but it should make the OD light flash because the computer can sense that the circuit is open.
That's good, I'll try that this afternoon. Once i know (i hope)it's somewhere in the wiring I can trace the fault.

Dave
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post #8 of 9 (permalink) Old 11-19-2009, 07:49 PM Thread Starter
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Re: TC locked in forward, OK in reverse, just changed solenoid pack

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Originally Posted by moore20017.3 View Post
Ford dealer in IL had called to tell me that my tranny was shot. I told him to unlock the TC switch and then try it out. lol It was doing the same thing you are seeing.

Is this truck new to you? Is it equipped with a manual TC lock switch?

If not, it sounds like a short in the harness as stated above. If you just purchased the truck, look for a TC lock switch, or possibly wiring for one that was not removed porperly and is grounding out.

The purple/yellow wire is the one for the TC lock BTW.
Mark and Moore20017,

It was the TC lock switch, after cutting out the wire were it was wired into the loom, everything is now OK!!

Thanks for the help!!

Dave (again a happy F350 owner!!)



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post #9 of 9 (permalink) Old 11-20-2009, 03:06 AM
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Re: TC locked in forward, OK in reverse, just changed solenoid pack

Quote:
Originally Posted by moore20017.3 View Post
Ford dealer in IL had called to tell me that my tranny was shot. I told him to unlock the TC switch and then try it out. lol It was doing the same thing you are seeing.

Is this truck new to you? Is it equipped with a manual TC lock switch?

If not, it sounds like a short in the harness as stated above. If you just purchased the truck, look for a TC lock switch, or possibly wiring for one that was not removed porperly and is grounding out.

The purple/yellow wire is the one for the TC lock BTW.
Nice call.




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