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My 2008 6.4 F-250 4x4 truck wouldnt start today. I got under hood and jiggled the battery cables and got it to go. Drove home and tried a couple hours later. Nothing. Jiggled some more. Nothing. Jumped starter relay. Started perfectly. Shut it off and restarted several times with key. Waited 20 seconds and tried it. Nothing. Turned key to on position, disconnected relay and reconnected, truck starts perfectly. After 15-20 seconds, nothing. Any takers?
Describe EXACTLY what you mean by "jumped starter relay". Which specific terminals?
Auto or manual transmission?
I jumped the wire next to the battery to the positive terminal. Automatic.
I wasnt showing any check engine lights but scanned it anyway and found a "UO 101" code which says it's a TCM miscommunication. Very wierd set of symptoms. Have to check fuse, etc, I guess.
So I finally located the TCM. After checking fuses and halfheartedly checking wiring, I went to salvage yard and got one for $100. After changing it, truck started right up.
Instructions:
These were put in from top-down before cab so not fun! 2 8mm bolts from top need to be removed. (I pulled my bracket down a little to get more room) Fish TCM towards the front, there is enough wiring to do so. Once free of bracket, there is a slide out connector on it. It has a half circle for grabbing. Try to wiggle it around a little because mine was full of dirt and would move without it. Tab should slide out a little over an inch. Once TCM is free, dont lose gasket and see where it is in case it falls out of connector.
Pics of pull out Connector part that you pull on. and location of TCM below drivers door in bracket.
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