TC refuses to lock up - how to troubleshoot?

[Wes]

We have a manual lockup switch but it doesn't do anything, the torque converter is not locking up at any time. The transmission shifts hard and other than the lockup it works well. Coolant running about 180 degrees, but that shouldn't matter with the switch. So far I've checked out the switch on the brakes (the one next to the brake light switch) and it seems ok.

My next guess is to pull the plug off the transmission and check it, but I'm not sure what to look for - should it have 12v when a lockup signal is present? Is there a way to check the solenoid? I assume it should just read close to 0 ohms?

 

[93ty475]

Re: TC refuses to lock up - how to troubleshoot?

i had that problem and it was the brake fuse under the dash iirc.....you might check the switches and whatever else that actuates when you step on the brake pedal...

 

[Wes]

Re: TC refuses to lock up - how to troubleshoot?

Well I checked the switch, I took it out and cleaned the contacts (they weren't very dirty though) and put it back in, it was working good.

I haven't heard of a brake fuse, but I will check all the fuses to see if any are blown.

 

[93ty475]

Re: TC refuses to lock up - how to troubleshoot?

Well I checked the switch, I took it out and cleaned the contacts (they weren't very dirty though) and put it back in, it was working good.

I haven't heard of a brake fuse, but I will check all the fuses to see if any are blown.

sorry, forgot to mention that my speedo wasn't working when i had that problem..... the brake fuse was located between the "instr lamps" and "heat a/c"....think it's for the brake lights....send me an email at utwtire @gmail.com and i can send you a few pages from the service manual regarding tcc electrical diagnoses....

 

[Wes]

Re: TC refuses to lock up - how to troubleshoot?

Houston, we have lockup!

Thanks for the diagnostic sheets. I went through and checked everything. Some interesting info, the solenoid always has 12v positive going to it (when the ignition is on) and during lockup the ground is connected to complete the circuit.

The ECM relies on several sensors to determine if it should activate lockup. When it does, it completes the circuit by grounding the solenoid.

The ALDL wire (where you connect the lockup switch) goes straight to the solenoid and overrides the ECM so it doesn't matter what coolant temperature is, what gear you're in, hell it doesn't even matter if the engine is running - it completes the circuit.

The solenoid must have at least 20 ohms of resistance or it can actually damage the ECM.

So I unplugged the connector from the transmission, and everything checked out good. When I activated the lockup switch, it was grounded. It had 12v of power. The solenoid had 26 ohms of resistance. So I didn't know what to think.

I reconnected it, put a quart of fluid in because it was a little low, and took it for a drive - and it worked! So the only conclusion I can come to is that there was a bad connection. It also said there must be enough fluid pressure in the transmission for lockup to occur, but I can't see being a quart low making any difference so I'm going with 'bad connection'.

Here's the diagnostic sheets

www.fivaxis.com/tcc1.gif
www.fivaxis.com/tcc2.gif
www.fivaxis.com/tcc3.gif

 

[SY2932]

Re: TC refuses to lock up - how to troubleshoot?

Vault.

 

[Wes]

Re: TC refuses to lock up - how to troubleshoot?

Crap. This thing is driving me nuts. It works sometimes, sometimes it doesn't. Seems like when it gets hot it stops working. I've messed with the connection and I'm pretty sure the connection is good.

When it works the transmission works flawlessly, the lockup is solid - no slipping. And then it just quits. Even without lockup the transmission works perfect, hard hard shifts, no problems. I'm going to let it cool down and see if it starts working again.

 

[Ian Turgeon]

Re: TC refuses to lock up - how to troubleshoot?

might want to make up a simple circut and leave it installed in the truck so you can help diagnose when if isnt locking up if the transmission is in fact not getting the signal. Just a simple LED or incondecent would work fine.

 

[Crimson93Ty]

Re: TC refuses to lock up - how to troubleshoot?

There are a couple switches and wiring up inside on the valvebody. Intermittent stuff is "usually" something electrical. Make sure the TCC wiring hasn't chafed on anything causing intermittent shorts to ground which could make the voltage go to ground instead of your TCC solenoid. I've found them by bending the wiring around and found brakes in the plastic housing that way.
The switch that has one contact doesn't do anything. I've traced that wire and it doesn't have a wire in the loom going to it on the connector itself. The other switch with two connectors is Normally Closed and opens the circuit momentarily when a sudden pressure increase is applied on a downshift. This opens the TCC circuit which reduces the load on the engine for a short time on downshift I think. If that switch is sticking open, you can get the same probelm. Maybe you can just jump those red wires together temporarily bypassing the switch to see if the problem goes away?

 

[Wes]

Re: TC refuses to lock up - how to troubleshoot?

I got a new solenoid today, I will check out the wiring when I put it in (it comes with the wiring so the wiring will definitely be good after I install it).

Took it for a drive today over to Hughes and here's what's going on - when the transmission is cold, it works fine. Lockup works perfectly normal. When the tranny gets to about 120 degrees it is so-so, I was on the freeway and holding the same speed it would unlock but if I gave it some acceleration it would lock back up. Then after the tranny gets to about 150 +, no lockup at all.

I talked to the guy at Hughes he said it's a good possibility that it's the solenoid, I guess I'll find out soon. If it still doesn't work I will try bypassing that one switch you mentioned.

 

[Crimson93Ty]

Re: TC refuses to lock up - how to troubleshoot?

I wonder if as the solenoid heats up the resistance is building until the solenoid no longer works. I've never heard a bad thing about Hughes. Hopefully you get fixed up soon. :tup:

 

[Wes]

Re: TC refuses to lock up - how to troubleshoot?

Got it working finally! I put the new solenoid in AND bypassed the 4-3 switch, so I'm not sure which was the problem but I'm sure it was one of them. It's working fine now, I did get a couple hickups while cruising on the freeway so I'm not sure what that's about but other than that the lockup is solid.

By bypassing the 4-3 switch, the converter stays locked up when your in 4th gear and you floor it and it shifts into 3rd, this might be a tad harder on the tranny but I don't think it will hurt it especially since it's built.

 

[Crimson93Ty]

Re: TC refuses to lock up - how to troubleshoot?

Purty :tup:
That's how mine looks. Driving in Ky on the hills had mine locking and unlocking all the time and was really annoying. Bypassing that switch eliminated a lot of that. Especially when your using cruise control. Nice pics
When you floor it, depending on initial throttle position, it should be doing a 4-2 shift. Slight increase in throttle should do a typical 4-3 though.
I could tell a 4-2 on mine because of the longer delay. Most noticeable when merging onto the highway
I had to play with my wastegate adjustment a tad after doing this mod initially. I was getting some small boost spikes on downshift that was getting a little knock retard. I also turned up the fuel a couple pounds and it went away.