TCC problem (TCC and EGR relay)?

[Peer81]

Hello everbody,

I was under the impression I fixed the TCC by putting a new wiring harness in the 700R4 but the lockup still is not working.

In short how the TCC system works.

At the transmission you have 3 wires. A, B and D.
A gets 12v from the ignition to power the lockup solenoid, that is all it does.
B is the high gear input for the ECM (i'm not using this one).
D is the ground wire for the solenoid. But this is how it works. Under 30mph and when braking this wire also has 12v on it.

With 12v on both ends of the wire the lockup solenoid doesn't work, it only works when wire D is grounded.

My problem is wire D almost never grounds so the lockup solenoid doesn't energize.
When I look in my shopmanual on page 6E1-41 I see the tcc and egr relay in the picture. When looking at the wiring diagram on page 6E1-45 or 8C-38 (near the middle) I think the tcc solenoid is controlled by the tcc and egr bleed relay. It looks like the tcc bleed relay and the air switching relay are the same so I could change them to check the relay right? (or checking the relay by itself..)

And if I'm right then power comes from ignition 1 travels through the brake switch to the tcc bleed relay (wire 420), on the way back (wire 922) goes to the ECM TCC terminal. So I think the ECM sets the minimum speed by grounding the wire above that speed and the brake switch interupts the current in wire 420 unlocking the relay. When the relay is energized wire D (wire 422 in the diagram) from the lockup solenoid is connected to wire 450 inside the relay and wire 450 goes to the ECM as power ground.

So my question were does the 12v come from in wire D?
As my EGR and AIR system is all show but doesn't work could this effect the TCC bleed relay?


Well, I think I'll start with checking and switching the relays around. All comments are welcome!

Greetings Peter

 

[TimAT]

IF the ECM does not see 4th gear, it won't know when to command a ground. Lockup is also dependant on engine temp. If it (engine temp) is too cold, and the TCC locks, it'll shudder and feel like the engine is stumbling.


(That's digging up my really old memory.)

 

[Peer81]

Thanks Tim, I'll look into it!

Tonight I'll try to check the tcc bleed relay if it still works.
As the tranmission only has plase for one switch in the valvebody I used it for a 2 prong 4th gear switch. So now I don't have any place to connect the high gear lead to. I'm wondering if it would effect anything if I would permanently ground the high gear wire? Or find some way to ground it automaticly at the right moment?

Greetings Peter

 

[Peer81]

Small update on this one.

TCC solenoid is still not locking up.
Almost everything checks out. 12V on the solenoid to the TCC relais (to dead terminal).
12v from brake circuit to relais core. From relais core goes a ground wire to the TCC terminal on the ECM and is not working.
When the relais core should energize the relais switches from the dead terminal to the power ground terminal so the solenoid will lockup.

Problem is still, whatever I do, I can't get the TCC ecm wire to ground.
I don't know if the high gear switch in the original 350c is NO or NC. As I don't use the wire anymore I grounded the high gear wire for the first test (and at the second test disconnected). Rear wheels from the floor and speeding up to 50mph. Still no ground signal, engine was at operating temp.
As I did get a ground signal from it a year before I'm thinking maybe I short circuited the TCC input to the ECM. Does anybody know if this wire has a fuse? I can't find anything TCC related on the fuse panel.

Thanks,

Greetings Peter

 

[navy2kcoupe]

Hello everbody,

I was under the impression I fixed the TCC by putting a new wiring harness in the 700R4 but the lockup still is not working.

In short how the TCC system works.

At the transmission you have 3 wires. A, B and D.
A gets 12v from the ignition to power the lockup solenoid, that is all it does.
B is the high gear input for the ECM (i'm not using this one).
D is the ground wire for the solenoid. But this is how it works. Under 30mph and when braking this wire also has 12v on it.

With 12v on both ends of the wire the lockup solenoid doesn't work, it only works when wire D is grounded.

My problem is wire D almost never grounds so the lockup solenoid doesn't energize.
When I look in my shopmanual on page 6E1-41 I see the tcc and egr relay in the picture. When looking at the wiring diagram on page 6E1-45 or 8C-38 (near the middle) I think the tcc solenoid is controlled by the tcc and egr bleed relay. It looks like the tcc bleed relay and the air switching relay are the same so I could change them to check the relay right? (or checking the relay by itself..)

And if I'm right then power comes from ignition 1 travels through the brake switch to the tcc bleed relay (wire 420), on the way back (wire 922) goes to the ECM TCC terminal. So I think the ECM sets the minimum speed by grounding the wire above that speed and the brake switch interupts the current in wire 420 unlocking the relay. When the relay is energized wire D (wire 422 in the diagram) from the lockup solenoid is connected to wire 450 inside the relay and wire 450 goes to the ECM as power ground.

So my question were does the 12v come from in wire D?
As my EGR and AIR system is all show but doesn't work could this effect the TCC bleed relay?


Well, I think I'll start with checking and switching the relays around. All comments are welcome!

Greetings Peter

Peter, look at it this way.. Pin A is one side of a continuous loop of wire called the lockup solenoid. Pin D is the other side of the solenoid. If the solenoid is good, there is continuity from one side, thru the solenoid to the other side. If you measure from pin A to ground, you get 12 Volts. If the solenoid is good, measuring from pin D to ground SHOULD show 12 volts, unless something grounds pin D. I guess you might be able to do this........ There are 2 sides to that connector. One side goes to the solenoid, and the other goes to the wiring harness. Remove the wire that goes to pin D in the harness side. Install a separate wire into that position, and wire it to one side of a normally open push button switch. Wire the other side of that switch to ground. Plug the 2 sides of the connector back together, and when the button is pushed, the converter SHOULD lock up. When the button is released, the converter SHOULD unlock. To automate that function would require a relay used in conjunction with the brake light. You would have to manually lock up the converter, and applying the brakes would unlock it. Then you would have to manually lock it up again and so on. The ECM, TCC relay, and EGR relay sound like they do that function and then some.
Andy

 

[Peer81]

Hello Andy,

Thank you for the clarification
The only problem I have right now is; Why isn't my TCC terminal at the ECM not grounding when it should? Could I have damaged it at some previous attemps?
I checked the TCC terminal wire at the TCC relais and not a the ECM. Maybe I have a broken wire but I don't think so.
If somebody could help

Groeten Peter

 

[navy2kcoupe]

The TCC terminal at the ECM should go to ground when ALL of the inputs to the ECM are in their correct states. Like speed above 40 MPH, trans in high gear, brakes NOT applied, and all of the other conditions that GM has programmed into the TCC circuit. If the TCC terminal is not going to ground, then one (or more) of those inputs are not correct, OR....... the ECM is bad. You're going to have to make sure that ALL of the parameters for lockup are being met, and fix them if they aren't. If all of the parameters are correct, then I would suspect the ECM. Good luck with it, and I hope you find it quickly! There isn't too much time left to drive it before the cold weather sets in and you either have to drive it in the snow, or keep it in the garage. :L
Andy

 

[Peer81]

Thank you Andy and Tim,

Yesterday I first drove the car for 30 minutes and then tested the TCC wire and yes above 40 mph the wire goes to ground! I think the engine wasn't warmed up properly the other times. Or maybe the ECM is also looking at oil temp and not only the coolant temp?

Also found out the high gear output used to have a NO switch. Most partwebsites show the high gear switch as a NC switch but on mine it isn't. Don't side is that on my MD8 700R4 I didn't have any place to put a high gear switch so I didn't connect the wire. I think it would be the cleanest solution to put the high gear wire on continues ground inside the automatic but connecting it to ground outside the automatic is alot less messy!

So I'm happy the problem was my own inpatience and not a broken ECM

Greetings Peter

 

[GerryLP]

I always thought the ground was provided by the pressure switches. Once hydraulic pressure reach the switch setting, the contact would close, and ground the wire. The computer all it does is detect the switch action, and apply the ground to where is needed. :ugh

 

[Peer81]

Almost Gerry,

But the shop manual wiring diagram gives you a great view on how it works.
Btw. without the lockup I was driving 120km/u at 2000 rpm. With the lockup applied the car is running 1850 to 1900 rpm at the same speed.

Greetings Peter