4T60E transmission temp sensor

clutch492 · 11-28-2009, 12:38 AM

I have a 1994 grand Prix. It has a 3.1 engine. This summer (while hot outside) the transmission started acting up. I am an ASE certified auto mechanic and should be able to fix this issue myself fairly easy, but I am wondering if anyone thinks that I am on the right track. Here is what it is doing...... While in overdrive and doing around 60 MPH, the TCC stops working and soon after the overdrive falls. It then reverts to 3rd gear and will not shift back up to OD. I stop for about 30 minutes to have a bite to eat and get back on the road....... overdrive and lockup works again (for a while) then fails again.

I have replaced the solenoids (thinking the TCC solenoid was bad). I replaced all the solenoids and the PWM. It still does the same thing after it get warm.

Is there a temperature sensor? Can it be bypassed? Is the temp sensor causing the problem? I ask this because it is heat related (as far as I can tell).

Thanks ahead of time for all your help.

CrazyHorst · 11-28-2009, 07:59 AM

One idea is to hookup say a voltage gage to the solenoid(s) in question.

So then you can see if the activity is being "commanded".

I am wondering if a vehicle speed sensor or ERPM sensing is not working correctly.

Seems like this was around the time frame of the EC^3 (Electronic Converter Capacity Clutch or Electronically Controlled Converter Clutch - I forget which right now) which basically uses a pulse-width modulated pressure to control the TCC clutch. The idea is instead of locking up the TCC "solid" it allows the two sides of the clutch to slip in a controlled manner with about 5 rpm difference, all in the name of getting better damping thru the driveline.

I'm not 100% up to speed on the details of how the strategy works past that but any error in speed sensing is probably going to kick it back into a "normal" mode where clutches are in a normal and locked state. One side is probably related to Eng RPMs and the other is probably sensed in the transmission but not sure where.

tblake · 11-28-2009, 06:13 PM

Sounds to me like your trans is reverting to LIMP IN mode. Have you checked the trans connectors for corrosion and made sure the grounds were good?

troy1 · 11-29-2009, 11:26 PM

A bad range sensor can cause your issue

clutch492 · 11-30-2009, 12:41 PM

This is the cure for this issue: Either replace the temperature sensor, or (since it is my own car) jumper out the temp sensor. Here is what I discovered..... This car has the 2nd gear start. With this model, there is a temperature sensor located inside the side cover. It will cause the transmission to go into "limp-in" mode (1, 2, and 3 only) to allow the engine to run at a higher RPM to cool down. Well, there are 2 wires on the harness that are devoted to the temp sensor. I had another temp sensor from another transmission and I test it. It had 3K ohms resistance at room temp. I then added heat to it from a blow dryer. As the heat rose, the resistance went down to .9K ohms. So, I found a resistor that had 3K ohms resistance, cut the two wires on the outside harness and soldered it in place. This will tell the computer that the transmission is cool all the time. (it is my own car) I would not do this to a customer car (but it does work). Thanks for all your replies.

tblake · 12-01-2009, 02:08 AM

Thanks for the follow up. Its a good idea to do this for diagnosis, but I don't think I'd do it to my own car unless I'm in a pinch. Pulling the sidepan of the trans shouldn't be a big issue for an ASE certified tech!! HAHA! No but seriously, if your going to run with it like that, it might be a good idea to install an aftermarket trans temp guage so you can keep an eye on things.

Bearwulf · 12-01-2009, 03:13 AM

How many miles since last service?

clutch492 · 12-01-2009, 11:12 PM

I figured I would catch some flak for this one. But, since I already had the side pan off once and replaced everything "but" the temp sensor, I just couldn't do it again. I may change my mind and tear it down again. And, yes, I do have a lift and all the tools to do the work, just need more time.

I enjoyed the statement from tblake. You are great, and you are right.

tblake · 12-02-2009, 08:17 PM

HAHA, yeah sorry! I couldn't resist! You can slam me whenever you want and I wont get mad!

I completly understand on the time issues. I just dont have time for things anymore either, especially nowasays. If this is your only driver, I dont blame you for wanting to get it going as quick as possible. I just dont think I'd be able to be without a vehicle for a day for a big job like taking the sidepan off.

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