90 Buick LeSabre 4T60 Trans TCC solenoid question

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#1
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MAKE: Buick
MODEL: LeSabre
YEAR:1990
MILES: 91,000
ENGINE:3.8
DESCRIBE ISSUE....Neighbors car (used to be mine several years ago) goes in and out of TCC lockup 50-60 mph. No codes. I disconnected TCC plug on this 4T60 (THM440-T4) Trans and problem is gone and now, of course, check engine lamp comes on and off.

How do I know if this is the TCC solenoid, the switch on the brake pedal. or the ECM or ?
 

nickb2

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#2
Try this TSB, sounds alarmingly similar to what you describe.


Solenoid may not even be in problem.

But to check the solenoid, here is the procedure.

No resistance values at all could be found. May be BP can chime in here.

Screenshot (795).png Screenshot (796).png
 

billr

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#7
Does your scanner show live-data for the trans? My Snappy does, and it is old enough to connect to that '90. I would first look for what the TCC is being commanded to and the brake status is.
 

nickb2

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#9
I always try to provide the most info for those that don't have a scanner.

Bust basic DVM should do if you follow the wiring.

Jackc is a wrench and he will have all my help. Normal.
 
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#11
Thanks Nick and Bill.

My OTC system 2000 scanner does not go past 1989, but since everything on the 90 seems identical to my 89 I am sure it works OK. In fact I have used it on the 90 many times when I owned it. BUT it does not show live data for trans. In fact it only has the one TCC code listed, which is 39 and simply states TCC. Nick's pdf above helps with that. But it doesn't throw a code when connected.
I do have friends at Trans Pro Walnut Creek that may be of help. Their shop was next to mine 35 years ago. I will see if I still know anybody there. ;)
I may also install an off-on switch on the dash, so he can turn off the TCC when he wants to. I have had a switch like that on my 89 for years so I can turn off that annoying TCC shift feel on slightly hilly mountain roads. If memory serves, I simply placed a switch on one side of the brake TCC switch. BTW that switch when off does not throw a code on my 89.
 

bp042665

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#14
i have seen this many times and have found that the tps sensor has a what i call a flat spot at mid throttle but i have found that with live data you can see that the computer is commanding it on and off
 

nickb2

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#15
@BP, no disrespect from me. But if Jack says the issue goes away with the TCC connector unplugged, so to say, wouldn't that just prove that the TPS is fine?

I am seeing less and less of these cars, so every bit of info I can get is great.

I disconnected TCC plug on this 4T60 (THM440-T4) Trans and problem is gone and now, of course, check engine lamp comes on and off.