Tcc Not Engaging

HDdave · July 11, 2007

Well I have noticed that I can never get the torque converter clutch to engage when my truck is in overdrive. I finally took it in to a tranny place and he took it for a drive with his snap-on scanner.. There is nothing at all internally wrong with the tranny, he just said that the computer is not even trying to send a command to the converter to engage the clutch.. Being a tranny guy, not electrical, he said that he has no clue what could cause the command not to be sent to the converter. On the random occaisions when the converter does lock (I guess that sometimes the command does get sent) I notice about a 500rpm drop, which if I can get this problem fixed should really help my gas milage. I was just wondering if anyone has a clue what could cause the computer to just not send the code..

Genuinefine409 · July 12, 2007

I could be wrong here but maybe the TCC selonoid is bad. You would think that the computer would still at least try to send a signal but maybe if it senses the TCC is bad it won't. I'm not sure if you can check them or not, I know in the 4L60E's a lot of the selonioids can be checked. What Snap-on scanner was he using, the one I use can force the TCC on under functional tests menu. Did he try that? What trans do you have?

sonjaab · July 12, 2007

Isn't the converter unlock/lock? triggered by the brake light switch when you hit the

brake? I have read of some of these issues caused by a bad switch.................

Thoughts???????

Genuinefine409 · July 12, 2007

Isn't the converter unlock/lock? triggered by the brake light switch when you hit the
brake? I have read of some of these issues caused by a bad switch.................

Thoughts???????

Now that you mention it I do remember seeing something about that. I had a 4L60E with no TCC engage and that was one of the things I checked. Mine turned out to be a seal the guy forgot to install cause the transmission was just rebuilt and after rebuild I have no TCC lockup. He made me check everything out saying it was something I did wrong and here it was his fault.

If you can get the scanner hooked back up you should be able to see on their under one of the data lists if the brake switch is open or closed. I'm not sure which menu but i know its in there somewhere.

HDdave · July 12, 2007

I remember he checked the brake switch and he said it opens and closes. He did have the snap on scanner that will engage the TCC because he did that several times trying to see if he could get the computer to send the signal.. Its a 4l80e tranny by the way.

HDdave · July 15, 2007

Does anyone else have any thoughts? Like I said, the brake switch was reading open and closed on his scanner, so that rules that out. My girlfriends dad used to work at a GM dealership and he thinks it could be a bad ECM. We looked for it yesterday and we think that the ecm is the black box located directly above thew foot heating/ ac vent for the drivers feet. Is that correct? Today we are going to take it out of that location and take the truck for a drive then smack the ECM with a screwdriver or hammer when were driving. He said 9 times out of 10 if it is a bad ECM then when we hit it, it should engage the clutch. Other than that, we don't have the slightest clue what it could be. I mean I guess I could take it to a dealer, but they would just charge me a rediculous amount and maybe not even find the problem....

sonjaab · July 15, 2007

Take it to one of the "big box" parts store. Most will run a free code scan for ya!

HDdave · July 17, 2007

I have done that several times... Only codes are a bad fuel pump sending unit (explains why my gas guage doesnt work), and a random cylinder misfire which is just an injector. No codes at all for the tranny. We tried hitting the ECM, and that did nothing. Someone on here has to have a guess at what it could be.... My last resort that I can think of is just buy a Predator programmer, which I was going to do already, and see if that fixes the problem...