t/c unlocking
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Junior User
Joined: Aug 2006
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t/c unlocking
i think my t/c is unlocking /locking at any speed with the cruise control on or off the tach bumps up 200/300 rpm,it did not seem to do it if i stayed in 2nd but i didnt drive it that far in 2nd, my brake lights are all working and the cruise does not kick off when it is doing it,is the t/c shot ? is there something eles i can try? thank you.
Lead Driver
Joined: Nov 2003
Posts: 6,900
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From: Campbell River, B.C.
Originally Posted by ola1234
I had something like you explain. At mine it turned out to be a bad connection to the speed-sensor.
bobpat204, on your year of truck the speedo is electronic and it shares the same sensor as the tranny, and if the sensor is not working proberly, then you should notice the speedo acting funny.
Now does this failed lockup happen consistently at any speed where you would normally be locked, or is it only at specific speed(s)?
Will it stay locked under any conditions at all?
Senior User
Joined: Jul 2007
Posts: 118
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From: Winthrop, Minnesota
You may want to pull the diagnostic codes. They will eliminate a lot of guess work. I had a similer problem on my 90 f250 E4OD and it turned out to be a FIPL that was sending intermitant signals to the TECA which inturn was sending commands to the TC to lock and unlock as I was driving the truck. I showed up as continuous memory code 63 if i remember correctly. Good luck. Jim
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i have similar thing with mine BUT it is intermittent. as in it will do it one day then not for 3 -4 days. if it is doing it, it will do it whenever i hit a bump? i figure its a loose wire somewhere but dont know where to look. also my tach goes up and about 200 rpms but my speedo remains the same but then it ( the TC ) will re-engage and go back to the right RPM until the next bump....
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Senior User
Joined: Jul 2007
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From: Winthrop, Minnesota
To pull or read the codes you either need to buy, beg, or borrow a OBD1 code reader. Or if you live near a Autozone they may be able to read your codes for you. I bought a OBD1 code reader made by Innova Electronics from Kragens Auto Parts for $30 plus tax. By the way OBD1 is for 1981 to 1995 Domestic Fords. Also if you want to do the Key On Engine On test by yourself you will need to buy the 6ft. test cord or do what I did which was make one from some wire and spade connectors. It's not hard to do and it realy helps eliminate the guess work and unnecessary replacement of parts. Jim
Senior User
Joined: Jul 2007
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From: Winthrop, Minnesota
Yes it will still read codes even if your enigine check light is not comming on or the overdrive light is not flashing. I know that is not what the manuals say but when I was have problems with my TC locking and unlocking and the trany was shifting eratically the engine check light was not on nor was the overdrive light flashing. But I was still able to read the codes and deremined that in my case I had a bad FIPL sensor. Jim
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Joined: Oct 2005
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From: Powell River B.C.
I would pull and check for good grounds on all your tail light connections. Even though you brake lights are working, they may be finding ground though some strange other circuitry, or possibly any external lights with a bad ground is sending power back down the brake light circuit, confusing the PCM.
Senior User
Joined: Jun 2006
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Originally Posted by KJLYPW
I would pull and check for good grounds on all your tail light connections. Even though you brake lights are working, they may be finding ground though some strange other circuitry, or possibly any external lights with a bad ground is sending power back down the brake light circuit, confusing the PCM.