Transmission Control Unit TCU

I compiled from one known source following data on 'one page'. It happily contains some engine points also for verification.

To check those easily, one has to build/solder a parallel connector. Here is the pic of that under construction. Not necessary, but without it doing the measurements is a PITA.












Its now on: http://www.cardomain.com/memberpage/748507/15



Dont worry, be Happy!


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Excuse my ignorance,but what does a TCU do?
Will it work on a '90 auto?

 

It's just the computer that controlls your auto tranny.

My TCU just sits there wondering WTF is going on

 

T ransmission
C ontrol
U nit

...works for u transmission box [auto] so that you can relax, be ignorant and enjoy. Its already there

...sometimes happens that theres a problem. Then u need info. Its already been there; now there served like this

 

No, sir. He is waiting for u clutch to burn off...

 

I'll stick to my flywheel and clutch but

 

Hey u are young and virile. Me ol and ti re d.

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Here's what -NEWS to ME- I found last night:


Went testing yesterday, 28F, tranny at 72F at startup:

It took 20miles drive at 60mph to warmup the tranny. After that the lockup preformed perfectly.

The voltages are about the same as the FSM list indicates, maximum voltage readings were about one volt less than battery voltage at that point.

The pin21 which should be the TPS "kickdown" switch:
I have found at least three kinds of wiring diagrams on this Throttle Position Sensor switch. In one of them, this Wide Open Throttle Switch -wire ends in a nowhere 'butterfly' ...whata laugh!
Also Nissan FSM tells that this is "not used" ...quite strange. But that pin is absolute zero grounded, and does not do anything in my car! Still measurements at TPS tell the switch itself is functional.
Must be so that different TCU versions use this TPS for TCU shiftdown, but some other models calculate the speed how fast accelerator pedal is pressed, which is the case in my car as the tranny functions perfectly.

?Why I did all this troubleshooting? The reason was intermittent gear lock problem [now vanished after tedious cleaning TCU connector with cleaner]. This lockup locks gear 3 or 4 on higway, so that turbine is bypassed. This results in 10% less fuel consumption. Notice that it needs up to 20 miles drive first to become functional [tranny temp up], and that starting from garage!

seen also at : http://www.cardomain.com/memberpage/748507/15

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Yeesh... You should have just asked about that one... I could have told you it takes that long to warm up and lock up the tranny if you're starting on a cold day. It will slip in 4th gear until it's fully warmed up, then finally lock up about 20 minutes later (as you've seen and tested).

 

The whole process started from intermittent loss of locking on a long trip (last week hollered here hlp). This was just a end-note of TCU-digging: anyways I am saying that warmup for it needlessly long time. The overdrive comes in play much earlier.

Maybe ? some temp sensor trimming would help...

I am not absulutely sure if that [lock] problem is over yet, but seems so as it is like clockwork now.