how bad of a job is it to replace the tcc. i had my car scanned with a snap on scanner because when my car warms up, it idles real low and sometimes goes dead at red lights. im really more concerned of the tranny going out later on after the fluid is changed when doing the tcc.

 

The TCC is part of the torque converter, it's not replaceable separately. The good news is that a scanner can't diagnose any problems with it.

 

is it possible the tcc is bad and the transmission still shift good?

 

It's extremely unlikely that the TCC has failed in any way that causes your problem.

 

I think there's a bit of confusion here.

TCC (around here) means Torque Converter Control. The torque converter for a 700R4 is a "locking" converter - when in 3rd or 4th gear, when there is little load, the torque converter (TC) will "lock up". Locking up means that ... a solenoid inside the transmission opens a small valve, and the transmission pumps all the fluid it can into the TC.

The TC is two pieces, one inside the other. Both have fins like a turbine, and there is transmission fluid in there. The motor half turns, and the fins spin, which 'spins' the fluid around in a circle. When enough torque is applied from the motor, the fluid will 'catch' in the fins on the transmission side, and thus start spinning the transmission half. Naturally, the more fluid inside the TC, the easier it is for the engine half to 'spin' the transmission half - when the TC is full of fluid, the two halves will spin at the same rate with no power loss do to sloshing of the fluid (all fluid and no 'air space' means no sloshing).

Now - the TCC is a function of the ECM - the computer sends the signal to the solenoid in the transmission to activate, and thus open the valve and force as much fluid as possible forward into the TC. The ECM is programmed to only send this signal when in 3rd or 4th gear, and when there is a low load on the engine (ie not going uphill or trying to pass).

So, what happens 'normally', is that you leave a stop and onto the highway let's say, the trans shifts through 1st, 2nd, 3rd, then 4th - up until now you've been acellerating pretty rapidly (load on engine) to get up to speed to merge onto highway. You can see the shift on the tach (RPM's lower each shift). After you ease off the gas (you've reached 55mph), there is very low load, and the ECM sends the signal to lock the TC - you will usually see one more little drop in RPM's of about 100 - 300 RPM's - that's the TC locking up.

When coming to a stop, the transmission will downshift as you slow, when it comes out of 3rd to 2nd, or when the brake is applied, the solenoid controlling the TC lockup will release and the ECM will stop sending the signal ... and allow the fluid to flow back into the tranny thus 'unlocking' the TC so that it may once again 'slip' since there is less fluid and more air space for the 'sloshing' to occur inside.

It sounds like in your case, that it either locks and never releases, or that it is locked always.

BUT - there is nothing about any of that function that any scan tool can detect, except, maybe if the ECM is not sending the signal to the solenoid (or is sending the signal to the solenoid always).

So - maybe what the scan tool is telling you is that it thinks your ECM is sending the signal to lock the TC when it's not suppose to. But this means there's something wrong with your ECM, and NOT the TC itself - the TC is simply a mechanical devise, nothing electrical about it, and thus there's no way the scan tool can give you any diagnosis related to the TC itself. Same with the solenoid - there's nothing that can happen to it that a scan tool could detect.

So, you do not have a problem with your TC or your solenoid. The problem is with the ECM itself maybe.

Here's a simple test - disconnect the square 4 prong connector on the side of the transmission - then drive the car. Does the symptom of dying at redlights go away? If so, then based on that scan tool telling you there is a TCC issue, I'd try another ECM. There's nothing that will be harmed by disconnecting that and driving.

But first, you might just kinda trace those wires from that transmission connector and make sure they are all good connections, nothing fried, nothing frayed, nothing grounding out anywhere.

I hope that makes sense and helps.

 

Torque converter clutch

 

thankyou, that makes more sense to me now.

 

a new computer and map sensor later, same results. only difference is the computer keeps throwing a code 25. new map, new ecm, and electrical connections are good. what gives?

 

anybody?

 

lets try at night

 

bump

 

still looking for ideas.