Prior owner of my Fiero said that he was having TCC stalling issues and that someone fixed it for him by unplugging the TCC. I assumed that was the case and never even bothered to check the plug. I went and bought a new TCC solenoid and did the swap and realized the plug was still connected when I started.
After replacing the solenoid and testing I still have no overdrive nor did it stall before or after the swap.
I have seen some threads about a 3rd gear switch, what does that look like and where can I get it? Is that the Transmission Pressure Switch on fierostore? http://www.fierostore.com/P...px?s=54858&d=371&p=1
Also if my cruise control is disabled when I tap the brakes is it safe to assume the brake switch is functioning properly?
I know I need to test if the TCC cable is even hot with ignition but the weather isnt nice right now and the car is outdoors.
I am missing nearly all of the baby fuses in my fuse box...but according to my shop manual it seems that the TCC goes through the Gauges fuse?
Shop manual also doesnt show what amps those fuses should be for the tiny ones.

The TCC is also controlled by the ECM. The car has to be up to a certain operating temp and at a speed above 35 mph for the TCC to engage Makes it difficult to check the voltages at the plug.
The 3rd gear switch is the mushroom shaped sensor located on the bottom of the transmission very near to the TCC solenoid mounting location inside the side pan.

That part looked good, but I guess it will be easy to replace if need be.
I drove quite a good distance home from my friends house that we did the repair at...with speeds up to 75 it never went into O/D.
I think I read something about testing for ECM signal from one of the ALDL pins, will have to rerun a search and see if I can find it again.
I guess I'll see what kind of testing I can do in the morning and report back.

Went through some threads and found a good one to go off of tomorrow: https://www.fiero.nl/forum/A...041015-2-052618.html

[This message has been edited by Haggerty (edited 11-20-2009).]

Technically, there is no overdrive on this transmission, third gear is 1:1... just the torque converter lockup which basically just directly couples the engine to the input of the tranny by stopping the slipping of the torque converter.

If you can get or build an ALDL interface box for a laptop you can use WinALDL to see of the ECM is commanding TCC lockup while you are driving. The ECM has to see that the coolant temp is up via the Coolant Temp Sensor in the lower intake manifold and road speed is up via the Vehicle Speed Sensor at the differential before it will send the signal to lock the torque converter, the brake pedal switch has to be closed, and the transmission 3rd gear pressure switch must also be closed in order to complete the path to the TCC solenoid. The only things that the ECM can actually monitor are the coolant temp and the VSS, the other two have to fall in line on their own.

I've also found that if the fluid level in the trans is a little low it can cause hit or miss issues with the TCC.

[This message has been edited by carbon (edited 11-20-2009).]

Trannys vary with the TCC and engine RPM. I have seen some that will show a drop of up to 400 RPM when TCC is locked and others with 150 RPMs or less. Easiest way to check is to drive the car when warm around 46 or 50 mph while keeping steady on the fuel, depress the brake pedal slightly and notice a difference in RPM on the tach. There should be a slight increase.

quote Originally posted by 2farnorth: The car has to be up to a certain operating temp and at a speed above 35 mph for the TCC to engage.

That's a good point. Unlikely, being its a Fiero, that its running cold, but perhaps if the thermostat is missing perhaps it could be.

I once had a car that had a TCC issue; the thermostat was stuck all the way open and even after hours of driving it would run cool for the ECM to enable the TCC.

I would check for 12V at the TCC terminal on the car side of the 203 connector - it should be 12V with the key on and go to 0 when the brake is pressed.

Just wanted to update that the light test worked on terminal F when going into 3rd gear.

quote Originally posted by Haggerty: Just wanted to update that the light test worked on terminal F when going into 3rd gear.

That tells us that you have power to the TCC circuit, the brake switch is allowing the power to pass through it, and the 3rd gear switch and TCC solenoid are working.

Last 2 causes are the ecm not providing the ground or the torque converter lockup clutch is bad and slipping.

Easy way to check is to ground terminal F and go for a drive. When you hit 3rd gear the TCC will either lock up or not. If it locks up, the ecm is not providing the ground (faulty ecm or possible bad sensor that tells the ecm not to lock up TCC). If it does not, then you most likely need a new torque converter.

quote Originally posted by fieroguru: That tells us that you have power to the TCC circuit, the brake switch is allowing the power to pass through it, and the 3rd gear switch and TCC solenoid are working. Last 2 causes are the ecm not providing the ground or the torque converter lockup clutch is bad and slipping. Easy way to check is to ground terminal F and go for a drive. When you hit 3rd gear the TCC will either lock up or not. If it locks up, the ecm is not providing the ground (faulty ecm or possible bad sensor that tells the ecm not to lock up TCC). If it does not, then you most likely need a new torque converter.

So instead of grounding terminal F to terminal A, ground it to the body?

quote Originally posted by Haggerty: So instead of grounding terminal F to terminal A, ground it to the body?

I prefer to use a known good ground, but terminal A should work as well.

quote Originally posted by fieroguru: I prefer to use a known good ground, but terminal A should work as well.

I connected a wire from Terminal A and F and drove for 13 hours to get to operating temps, TCC never locked

One of these days I'll test for power at the TCC plug on the transmission.

Well I finally got around to testing the TCC plug that goes into the transmission, it shows hot when iginition is on.
If the ECM shows terminal F hot while in 3rd gear is it still possible that the 3rd gear switch in the tranny is bad?
I guess the next possibility is the plug inside the tranmission, but I guess the only way to test that is tap into the wire while ignition is on and tranny cover is off...
I think its time for an LS4 with 4T65HD instead.

Drove about 1500 miles this week, was still able to get 20-25mpg doing 70 atleast.

One of the wires for the solenoid is connected through the 3rd gear switch. If the switch isn't closed the solenoid can't engage.