brake light circut preventing lockup? 47RH

ahale2772

ahale2772

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Oct 27, 2011
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this may be a shot in the dark, but Ive been searching for a few hours.

my truck, with a newly installed auto, is not hitting lockup.

OD works (that alone may prove this theory invalid)

but no lockup.

In my haste to swap the transmission from a 5 speed, I left the brake pedal out, causing the brake lights to stay on for a few hours. I noticed when I put the truck back together, that the brake light switch had a melted terminal, and the fuse holder was partially melted. ....that being said, everything back together, the brake lights work.

but could I be missing some PCM sense wire that may have melted?

AFAIK, the truck looks at the temp sensor, VSS, brake light switch, tach sensor, and TPS

otherwise, the transmission shifts perfect. manual lockup switch yields no lockup as well (I assume a manual switch over-rules any other sensor input to the PCM)

I'm sufficiently stumped.:nail:
 
Last edited:
65 views no help? :(

I now have a lockup switch wired directly to the transmission. (orange/black wire)

still nothing... must be the lock-up solenoid?
 
If you have it wired direct and it doesn't lock then I would swap the LU and OD solenoids
 
i have had that on a truck once. brake light switch died , no brake lights and the lock up didnt work , worth a try for the few buck to replace it
 
ahale2772 said:
65 views no help? :(

I now have a lockup switch wired directly to the transmission. (orange/black wire)

still nothing... must be the lock-up solenoid?
Click to expand...

Verify that the ground signal is making it down to the solenoids inside, but yes that is usually the next step. New solenoids come with the harness too if you can't find a break in the internal harness.
 
BlackSkyRacing said:
Verify that the ground signal is making it down to the solenoids inside, but yes that is usually the next step. New solenoids come with the harness too if you can't find a break in the internal harness.
Click to expand...

tested my switch, it does have a solid ground.

with the pan off, the lockup solenoid is clicking. with the key on, flipping the switch nets an audible click, but only once. flipping it on/off any more times gets nothing. I assume fluid pressure resets the solenoid?

now what? internal VB issue?

can anyone enlighten me on how the hell the lockup function works in the valve body? what does what? what function does the solenoid play?

I may just swap the whole VB out this weekend to something else.

yet again, I'm at a loss
 
The solenoid closes when grounded, causing pressure to build up and switching the valve for LU.

Is it a new TC?
 
^^ This, it does require hydraulic pressure to reset. I have had them still click, but the ball side does not fully close off the vent and switch the valve. Solenoids are considerably cheaper then an entire VB and should be tried first.
 
either way, I've got my old VB lined up that has a fresh bill of health from Tim at TRE, and is modified for 2nd gear lockup. I'm going to try that.

the TC is brand new
 
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