Transmission Too Hot error

[vic_m4]

A few days ago, just cruising and a "Transmission Too Hot" error popped up and car went into limp mode. It was only there for a not even 5 seconds and it went away.

Few days pass and the car drives perfectly normal and fine. I don't track the car, nor it's tuned, and I don't drive it hard. Later today, the error popped up again, goes away in a few seconds. Same as before, but now it's popping up regularly as I'm driving the car, just cruising. Goes into limp mode every time the error pops up. I'm getting it checked out in the morning, but any ideas of what it could be?

Only fault codes that showed up regarding the error when I ran diagnostics were:

40DE01: Coupling Temperature: Red Phase

Any feedback would help, thank you in advance!

[horsepower_and_hounds]

Check and clean your DCT cooler.....it is a junk catcher

[Info@mad-us.com]

Clutch slip would cause that

[ALCOBENDAS]

I think there is a sensor that a lot of people gave temperature failure..

[Info@mad-us.com]

Originally Posted by ALCOBENDAS

I think there is a sensor that a lot of people gave temperature failure..

There is yes.

[Jim45678]

Originally Posted by vic_m4

A few days ago, just cruising and a "Transmission Too Hot" error popped up and car went into limp mode. It was only there for a not even 5 seconds and it went away.

Few days pass and the car drives perfectly normal and fine. I don't track the car, nor it's tuned, and I don't drive it hard. Later today, the error popped up again, goes away in a few seconds. Same as before, but now it's popping up regularly as I'm driving the car, just cruising. Goes into limp mode every time the error pops up. I'm getting it checked out in the morning, but any ideas of what it could be?

Only fault codes that showed up regarding the error when I ran diagnostics were:

40DE01: Coupling Temperature: Red Phase

Any feedback would help, thank you in advance!

vic_m4

hi Vic, have you fixed it? If yes what was the solution?
Have you replaced the sensor?
If yes, have you checked if the sensor was giving proper temps or it was stuck with some random temp?

[vic_m4]

Originally Posted by Jim45678

vic_m4

hi Vic, have you fixed it? If yes what was the solution?
Have you replaced the sensor?
If yes, have you checked if the sensor was giving proper temps or it was stuck with some random temp?

Turns out I just needed to change the trans fluid and the filters. It was changed at around 42k miles. I was afraid it was the sensor at first as well. But I've had the car back for over a month and the error has not came back since the fluid change. Hope this is just the case for you too!

[Jim45678]

Originally Posted by vic_m4

Turns out I just needed to change the trans fluid and the filters. It was changed at around 42k miles. I was afraid it was the sensor at first as well. But I've had the car back for over a month and the error has not came back since the fluid change. Hope this is just the case for you too!

Great! lucky you changing Oil solved the issue.

I'm wondering if you have monitored sensor of transmission oil temperature? Mine seems to be working correctly. This morning it shows around 28"C and engine OIL around 23"C. Once the error pop's-up I have stable 80"C on the sensor.

[vic_m4]

Originally Posted by Jim45678

Great! lucky you changing Oil solved the issue.

I'm wondering if you have monitored sensor of transmission oil temperature? Mine seems to be working correctly. This morning it shows around 28"C and engine OIL around 23"C. Once the error pop's-up I have stable 80"C on the sensor.

Well, back here again lol. The error decided to come back late at night at a stop light. I replaced the trans oil cooler thermostat, and that didn't solve the issue as the error came back again. It's only at 43k miles, I doubt I need a new transmission this early on, no? Did you end up solving the issue?

[vic_m4]

Bump. Has anyone experienced this issue?

Have done a full trans flush, and car was fine for about month and a half. Error came back and I replaced the trans oil cooler thermostat, which still did not work.
Car only has 43k miles, and I'm not slipping any gears. Doubt I'll need a new transmission this early on.

[Jim45678]

Originally Posted by vic_m4

Bump. Has anyone experienced this issue?

Have done a full trans flush, and car was fine for about month and a half. Error came back and I replaced the trans oil cooler thermostat, which still did not work.
Car only has 43k miles, and I'm not slipping any gears. Doubt I'll need a new transmission this early on.

Yep, i replaced oil, filters, oil pan, clutch temp sensor. Clutch was verified and it was ok. I hope it wont come back again because it was a really costly experience

btw: which sensor did you replace? there are three of them as far as i know? In my scenario it was clutch temp sensor. I hope i wont see this agan after a month.

[vic_m4]

Originally Posted by Jim45678

Yep, i replaced oil, filters, oil pan, clutch temp sensor. Clutch was verified and it was ok. I hope it wont come back again because it was a really costly experience

btw: which sensor did you replace? there are three of them as far as i know? In my scenario it was clutch temp sensor. I hope i wont see this agan after a month.

Yeah I replaced all of that, except for the clutch temp sensor. I ended up replacing the thermostat for the transmission oil cooler, which did not solve the issue as well.

Hopefully it fully resolved for you!

Btw what was the process in replacing the clutch temp sensor?
Also, do you have a part number for it?

[Jim45678]

I don't know exactly how the process looked like but when I was driving to the garage it popped up and we did quick error scanning. I guess the mechanic was using ISTA so he was able to read all three temp sensors. The clutch sensor was giving 161"C and that caused the error. Transmission temp sens was giving 81"C (same sensor bimmerlink is reading - you can't read clutch temp sensor with bimmerlink ).

He also double checked the clutch but it was like new. So I strongly believe and pray that it solves the issue and I won't need to do anything else. To replace this sensor they needed to dismantle the gearbox from the car.

If I'm correct this is the part number: #28107842851
https://www.hubauer-shop.de/de/drehz...107842851.html


PS: I had CS transmission/diff flash but it didn't help anyway. Its faulty sensor that needs to be replaced. Check with the garage temp of this sensor to make sure it causes the issue.

[BrickOwens]

I had this sensor replaced a few weeks ago and haven't had any issues since. A shop in the UK did a write up showing where the sensor is located in the transmission. https://www.munichpower.co.uk/bmw-an...rature-sensor/

[vic_m4]

Originally Posted by Jim45678

I don't know exactly how the process looked like but when I was driving to the garage it popped up and we did quick error scanning. I guess the mechanic was using ISTA so he was able to read all three temp sensors. The clutch sensor was giving 161"C and that caused the error. Transmission temp sens was giving 81"C (same sensor bimmerlink is reading - you can't read clutch temp sensor with bimmerlink ).

He also double checked the clutch but it was like new. So I strongly believe and pray that it solves the issue and I won't need to do anything else. To replace this sensor they needed to dismantle the gearbox from the car.

If I'm correct this is the part number: #28107842851
https://www.hubauer-shop.de/de/drehz...107842851.html


PS: I had CS transmission/diff flash but it didn't help anyway. Its faulty sensor that needs to be replaced. Check with the garage temp of this sensor to make sure it causes the issue.

What was the cost of labor if you don't mind me asking?

[Jim45678]

Originally Posted by vic_m4

What was the cost of labor if you don't mind me asking?

I live in Europe so prices are much different I guess. I paid around 700$ for labour itself. It was in the independent garage specialised in BMW only

PS: Funny thing this issue is related mostly to US cars. I checked local forums and no-one had such an issue with this sensor. Mostly its caused by damaged clutch due to hard usage but not due to sensor error. My car has only 33K miles and still original PSS tires

[SD ///M4]

I had this message come up as well on my '16 M4, mileage 48,230. I was driving normally, running errands on surface streets and I saw a message about "transmission temperature". It also said that driving was possible. Happened twice within a short period of time on the same day. Temps were in the high 60s/low 70s. The message went away so quickly each time that I didn't have a chance to snap a photo of the iDrive screen. Several weeks have gone by and I haven't seen it since.

Since I have the extended warranty and it was expiring soon, I took it to the dealer, and they diagnosed it as a "faulty combination RPM/Temp sensor" inside the DCT. They had to order the part but were supposed to complete this today. I dropped off the car last Thursday and had to go back today to retrieve some items in the car and the mechanic had the car up on the hoist. The bottom of the transmission was removed and there were some hoses disconnected. He said that the transmission had to be dropped. They said they were going to check the clutches. My cost is going to be the $50 deductible.

[Jim45678]

I wish I could pay only 50$ !

almost year later, heavy and aggressive driving no issues at all after replacing the DCT temp sensor

[RAT3DM]

I had the same issue which was caused by slipping clutch disc causing too much heat. From a driving aspect you could feel no slipping, but the sensor was doing it's job. If you replaced the fluid and sensor and still have the issue it's possible your clutches are already damaged and just continue to heat up your fluid.

[RIPAMG]

Originally Posted by BAD_M4

I had the same issue which was caused by slipping clutch disc causing too much heat. From a driving aspect you could feel no slipping, but the sensor was doing it's job. If you replaced the fluid and sensor and still have the issue it's possible your clutches are already damaged and just continue to heat up your fluid.

I had the samae issue today, when I just started the car, drove about 5 minutes. It was in 3rd gear, about 20mph... I don't think the clutch was slipping

[MannyJ96]

Originally Posted by vic_m4

Well, back here again lol. The error decided to come back late at night at a stop light. I replaced the trans oil cooler thermostat, and that didn't solve the issue as the error came back again. It's only at 43k miles, I doubt I need a new transmission this early on, no? Did you end up solving the issue?

Is this the same error message? I first got it a couple months ago in December 2023 then it went away. Came back again earlier this week.