Intermittant TCC Engage 4T80-E Trans.
 

I have a 93 Allante w/85K miles runs great accept for an intermittant tcc engage problem code po39. once set it disables the tcc for that engine cycle. I was told that I might have a tcc solenoid going out but all my tests dosn't seem to prove that. I do have a question . While driving I can enter diagnostics clear codes enter pcm override set mode to ps01 tcc and let the pcm control the tcc . by monitoring the status lights everything looks normal also I can monitor the slipspeed, turbine rpm,tps,and brake switch functions with no faults, manually disengage the tcc see the rpm rise ,slipspeed above 100-200rpm then release the disengage then let the pcm take control again and within seconds the rpm drops , slipspeed drops to 1 to 6 . and still holding my speed at 70mph , I can do this for miles on end . If I have a tcc solenoid going out it sure works ok in this mode . Any ideas thanks mike

the code is a general code and can be point to anything from slipping clutches to solenoids to a connector, a TPS or brake switch problem. I believe the code sets when the PCM doesn't see the expected RPM change when the TCC engages/dis-engages.

Also, those are very finicky solenoids if the fluid is even a few oz low.

Add a bottle of LUCAS, make sure your fluid is exactly at full MAX capacity, not even a tiny bit low.
At 85,000 miles, the LUCAS should be added no matter. It will help correct or prevent several age/wear related problems.

A failing solenoid usually drops the gear upon the slightest increase on power demand, usually even a slight incline on the road, but will do the same thing if it fluid starved or clutches are slipping.

Do the fluid thing with lucas, drive easy for 20 - 30 miles and see what happens. Dont drive it hard.

So you know, if a solenoid be needed, a willing TECH can R&R w/o dropping the transmission .


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