Another E39 P0740/F111 TCC Circuit Problem

[BimmerM3inGA]

I'm trying to properly diagnose a problem I'm having with a newly acquired 1999 528iT. I knew the car had some problems when I bought it (including this one), now I am trying to get it sorted out.

Here is some information on the car:
Build Date: 02/99
Mileage: 137,XXX
VIN: WBADP6332XBV61575
Transmission Serial #6194383

The car runs and drives great. The transmission shifts smoothly and I haven't noticed any slipping. In fact, if it weren't for the Check Engine light, I wouldn't even know there's a problem. I have another E39 528iT (09/98) and if I drive them back to back, I can't tell any performance difference. So, as far as I can tell, the transmission is working correctly.

But every time I reset the CEL, it comes back on within a few miles. If I scan it with my el-cheapo eBay OBD-II code reader, I get the following code:
P0740 TCC Circuit Malfunction.

If I scan it with CarSoft, I get this error under the EGS - Auto Trans section:
F111
111 Torque Converter Clutch

And INPA gives me this error:
111 Torque Converter-clutch / Gear check

Here is a screen capture from INPA showing the error code:


I know I have a GM transmission, and I know it's a 4-speed. But I'm not clear on the exact model. And I understand from research I've already done that the problem can be different things depending on which transmission I have, and its serial number. To the best of my knowledge, I have the A4S270/310R, although it seems to have multiple model ID's (such as 4L30E and A4S 310R). Are these all the same transmission?

As far as possible solutions, I am going to try the following in this order:

1) Check the fluid level and top it off if needed.
What is the proper fluid for this transmission? Can I just use Dexron III, or is there a specific fluid for this particular transmission?

2) Replace the Torque Converter Lockup Solenoid along with the fluid and filter.

3) Replace the torque converter.

4) Replace the transmission.

I am really hoping that #1 or #2 will take care of it. While I had it connected to INPA, I activated the TCC Solenoid and it did respond by clicking, but it was pretty quiet. How loud should it be? Also, it kept tick, tick, ticking (about 1 cycle per second) even after I disconnected it from INPA. It didn't stop until I started the engine and then shut it off. Is this normal operation?

Lastly, am I doing any harm if I continue to drive the car? As mentioned earlier, it seems to be shifting with no problems and I haven't observed any slipping. If the fault ends up being the torque converter, will transmission damage be likely if I keep driving it? Or, if the solenoid is the problem, can I damage the torque converter by driving it?

[I Shield I]

I am also very interested in this problem if anyone has any experience dealing with this please chime in! Getting the same code on my '99 528iA only engine runs smooth and no shifting issues either. Recently did have to do CCV replacement though.

[rf900rkw]

Let's start by comparing your two cars. Drive the car at a highway cruise speed. Maintain a steady speed for a few seconds to let everything settle into state. Now, *lightly* accelerate, as if you just wanted to pick up a mph or two. We call this crowding the throttle. On the car that is not setting a code, the engine RPM will stay locked in place as if you had a manual. The car setting the code will have the rpm shoot up 100 or more RPM. This is what's setting the code.

A GM 4L30E = BMW A4S310R

On your strategy:

1> no effect. If the fluid is low enough to cause a TCC problem, you will have major slippage in 1st and reverse.

2> possibly. Not very likely

3> highest probability

4> possibly. There are a few sealing rings and bushings that control flow that may be worn. But see below

And I will add 5> Restricted cooler. If there is a restriction on the discharge side of the TCC system, it can hold the clutch plate off.

Can you cause damage by continued operation. YES. While the TCC is engaged, the converter will no longer flow oil; the clutch plate seals off the flow path. So when engaged, cooler/lube oil is redirected around the converter. There is no new oil being introduced into the converter. If the converter is slipping, it is generating heat and it will overheat. seriously overheat. It can cause fluid to be expelled from the vent (#1 cause of fires in F150s). It can cause damage deeper in the transmission. And it kills your mileage.

Now that you've scanned and proven the fault to be real and repeatable, the next step is to check the fluid condition. We don't really care much about color... or even mild smell. Converter burnt fluid is the nastiest stuff out there. Some have called it a burnt pumpkin smell. I don't think that does it justice. It is a smell that will go right to your core and not leave for days. You *will* know. If you have this, then the transmission has been exposed to too much heat and will need rebuilt/replaced. The damage will be beyond the converter... every piece of rubber and plastic inside will be done.

[BimmerM3inGA]

Thank you for the information - exactly what I was looking for.

An update: A couple of days after after I posted the original message, the CEL turned off all by itself and stayed off for a couple hundred miles. This morning on my commute I tried your experiment: Cruising at a steady 60MPH I slightly crowded the throttle. The car accelerated a few MPH with no change in RPM. I can't compare the other car (the one not setting the code) at the moment because I'm having some paint work done.

On my way home, the CEL came back on while in stop and go traffic. Due to heavy and slow moving traffic, I wasn't able to try the experiment again on the way home with the CEL on. I'll try it again in the morning.

I have noticed that the light seems to come on at low speeds and when in traffic. Shouldn't it be coming on while cruising at a steady speed? Is the light triggered immediately when the problem occurs, or is it buffered in some way?

Also, you can see in the INPA printout that the transmission temperature at the times of the faults is always around 40ºC. It's my understanding that above 50ºC or so is considered too hot.

If I am dealing with the possible Scenario #5, what is the solution? How should the lines be cleared?

[rf900rkw]

40C is cold. Hell, your from Georgia, you ought to be used to 40C! The normal op temp will typically be between 80 and 110C. It may well be that the clutch is holding at higher temps and speeds, and only setting a code at low temp marginal low speed apply.

Scenario 5 is not a common problem. It was mentioned because it can and has happened. The two common causes of 5 are either the TCC broke up and the pieces have the cooler plugged, or someone re-engineered the system to make it better.

[BimmerM3inGA]

I thought the normal operating temperature is supposed to be 35ºC - 50ºC. 110ºC is awfully hot - above boiling. Is that really normal?

On my morning commute I tried the crowding experiment again with inconclusive results. At a steady 60MPH I gently increased the throttle and the car accelerated with a negligible increase in engine RPM. Out of 5 tries, it may have increased 100RPM or so, but the car also accelerated. There was never a time when the RPM increased without a corresponding increase in road speed.