Coolant temp and thermostat codes

[mKilgore]

My suspicion is similar to your above notations AndyW. Though I have no real knowledge, I believe that the computer has some logic that is coupled to the TSTAT position. When the TSTAT is fully closed, the logic has an expected delta that the coolant temperature should warm up to versus time. When the coolant temp does not meet that increase in temperature versus time (due to the CSF radiators increased efficiency) then the assumption is made that the TSTAT is not properly closed and flowing more coolant than it should. This is why you get the "TSTAT jammed open" code. Which makes sense, the car is trying to close the TSTAT but is not seeing the corresponding increase in coolant temp it is expecting and thus there must be a fault. However, none of that is true, it is simply that the radiator cools the coolant at a delta below the computers logic.

My experience with this is that it is a computer issue. Not a physical fault like the TSTAT or wiring. I admire your persistence, but unless you want to get into the computer programming of the DME and start messing with that then I would just tape off your grill and call it a day. You won't have to worry about having to stop and reset your car all winter.

[blue135]

Do these engines use an electronically controlled thermostat (actual movement governed by inputs from control source) or is the thermostat movement in response to temperature of coolant?

[AndyW]

Originally Posted by blue135

Do these engines use an electronically controlled thermostat (actual movement governed by inputs from control source) or is the thermostat movement in response to temperature of coolant?

My understanding is it is both. I read somewhere that the ECU can control +-20% of where the mechanical position is.

[AndyW]

Originally Posted by mKilgore

My experience with this is that it is a computer issue. Not a physical fault like the TSTAT or wiring. I admire your persistence, but unless you want to get into the computer programming of the DME and start messing with that then I would just tape off your grill and call it a day. You won't have to worry about having to stop and reset your car all winter.

But we do have people in this community that do know how to access and modify the DME...

[AndyW]

Originally Posted by mKilgore

My experience with this is that it is a computer issue.

The only thing that doesn't make sense is...why does the temperature sensor show a fault too? Why wouldn't the DME just let it continue to track actual temp? That part is really tripping me up in this hypothesis. If the temperature indicated a failure first (which I don't know how to check - which one comes first), that could cause the TSTAT to code. But, it still goes to a specific temp (226F), which looks suspiciously like a "on fail go to this value". It's also interesting that the temp sensor code is a Shadow (inactive) code. Every time. While the TSTAT code stays active.

The new TSTAT and pump came in, so, it'll be nice to get that refresh done. I guess I'll find out afterwards if it was done early or not...

[irie00]

hello andy. I have the same problem. error codes 348a and 293e. the fan runs on a cold engine at low temperatures. I replaced the sensor and the water pump, but the fan is still working. did you fix this problem? sorry for my English. greetings

[AndyW]

Originally Posted by irie00

hello andy. I have the same problem. error codes 348a and 293e. the fan runs on a cold engine at low temperatures. I replaced the sensor and the water pump, but the fan is still working. did you fix this problem? sorry for my English. greetings

Sorry, haven't replaced the pump and thermostat yet. Only the temp sensor.

[irie00]

Ok! write if you can fix the problem. I am curious if the thermostat replacement will help. I have no other idea for that

[AndyW]

Originally Posted by irie00

Ok! write if you can fix the problem. I am curious if the thermostat replacement will help. I have no other idea for that

So, water pump and thermostat replaced and...it now does it below about 55F...lol. So the pump appears to be stronger. I think mKilgore is correct: It's an ECU programming issue and the solution is to mask off one kidney grille half the year...

[Bullitt]

My car runs with the CSF radiator + the auxiliary water cooler, and there is zero protest from the ECU. Engine is N54 with MT.

I'm guessing it must be the programming for N55's and automatic transmissions...

[AndyW]

Originally Posted by Bullitt

My car runs with the CSF radiator + the auxiliary water cooler, and there is zero protest from the ECU. Engine is N54 with MT.

I'm guessing it must be the programming for N55's and automatic transmissions...

Likely true. But N54 also runs hotter so in this case that helps. My 335i is N54 AT and also has a CSF rad and dies not have the issue.

[chance91]

Originally Posted by Bullitt

My car runs with the CSF radiator + the auxiliary water cooler, and there is zero protest from the ECU. Engine is N54 with MT.

I'm guessing it must be the programming for N55's and automatic transmissions...

Hey everyone,

Just wanted to throw in some more information here. It routinely gets to -20 or -30 here. Its cold. We are at 120+ days without breaking 40F.

I put a CSF radiator in my N55 E series since my original cracked and its a good track upgrade, where I head 2-3 times a year.

I have the same issue. Replaced a few parts, same results. I did some digging and logging, watching with MHD, learning in ISTA, and here's what I can tell you:

The DME has a "temp map" that it follows, based on operating time and outside temp, where it expects the engine temp to be. When the CSF radiator overcools in the winter, the engine doesn't get up to temp, and the DME decides there must be a fault in either the wiring or temp sensor, or the thermostat. The codes 293E and 348A - Thermostat clamped open indicates the ECU thinks this, and is going to run the water pump and fan wide open.

If you monitor this in MHD, especially after 4-5 starts with code set, the temperature will increase by exactly 2 degrees over a set amount of time. You may reset the code, briefly see temps more in the 100* range, followed by it shooting up to whatever it was at last count.

Thus far, the only solution I know of is a grille block like some old diesel truck. A partial block of the kidneys reduces airflow, and allows the car to run at reasonable temps. I tried this on an 8hour trip last week with temps from -15 to about 30, and it works well.

Still looking into custom tune options to improve the cooling management in winter, even if we delete the code in the tune the temp needs to come up to operate efficiently.

Hope this helps.

[JRUSH]

Also experiencing this in cold weather with my N55 AT with CSF radiator.

Have you found a tuning solution?

Originally Posted by chance91

Hey everyone,

Just wanted to throw in some more information here. It routinely gets to -20 or -30 here. Its cold. We are at 120+ days without breaking 40F.

I put a CSF radiator in my N55 E series since my original cracked and its a good track upgrade, where I head 2-3 times a year.

I have the same issue. Replaced a few parts, same results. I did some digging and logging, watching with MHD, learning in ISTA, and here's what I can tell you:

The DME has a "temp map" that it follows, based on operating time and outside temp, where it expects the engine temp to be. When the CSF radiator overcools in the winter, the engine doesn't get up to temp, and the DME decides there must be a fault in either the wiring or temp sensor, or the thermostat. The codes 293E and 348A - Thermostat clamped open indicates the ECU thinks this, and is going to run the water pump and fan wide open.

If you monitor this in MHD, especially after 4-5 starts with code set, the temperature will increase by exactly 2 degrees over a set amount of time. You may reset the code, briefly see temps more in the 100* range, followed by it shooting up to whatever it was at last count.

Thus far, the only solution I know of is a grille block like some old diesel truck. A partial block of the kidneys reduces airflow, and allows the car to run at reasonable temps. I tried this on an 8hour trip last week with temps from -15 to about 30, and it works well.

Still looking into custom tune options to improve the cooling management in winter, even if we delete the code in the tune the temp needs to come up to operate efficiently.

Hope this helps.

[chance91]

Originally Posted by JRUSH

Also experiencing this in cold weather with my N55 AT with CSF radiator.

Have you found a tuning solution?

The only two solutions are either grill block your front bumper, which isn't a bad choice, use some black plastic and zip ties, block about 50% of the lower grill and you'll get warm enough for the ecm to be happy.

The only other solution is to get a custom tune via MHD, and have the tuner remove the codes 293E and 348A, theoretically fixing this. Can't test myself as I no longer have the car.

[Uncle_Shlick]

I have a 3 series 2011 335xi with the n55, manual trans. I’m also having this weird issue. I replace coolant temp sensor. Havnt replaced Tstat or water pump yet. However I have the stock radiator. I’m also having these problems. Do u block the intake scoops in the kidney grilles with tape?

[AndyW]

Originally Posted by Uncle_Shlick

I have a 3 series 2011 335xi with the n55, manual trans. I’m also having this weird issue. I replace coolant temp sensor. Havnt replaced Tstat or water pump yet. However I have the stock radiator. I’m also having these problems. Do u block the intake scoops in the kidney grilles with tape?

If you have stock radiator, I'd suspect the problem is actually the T-stat.

[Uncle_Shlick]

Even with it causing my temps in MHD to spike and for the car to go into a limp mode? Wouldn’t it just throw the thermostat code as well? I have every symptom you have. My car will get up to operating temperature as well.

[nissubaru]

Originally Posted by Uncle_Shlick

I have a 3 series 2011 335xi with the n55, manual trans. I’m also having this weird issue. I replace coolant temp sensor. Havnt replaced Tstat or water pump yet. However I have the stock radiator. I’m also having these problems. Do u block the intake scoops in the kidney grilles with tape?

I am also having this issue but with an N54, manual trans. Specifically I am just getting code 2EE3 and my fans go on full blast and I lose power. Stock radiator, but I did replace the tstat and waterpump a few years ago (30k miles ago). My battery is also new within the last 6 months. Also, my car is not stock, FBO with MHD stage 2+.

I first started having this issue last year, coolant temperature sensor was replaced on January 7, 2023 which I find interesting. I thought maybe I replaced it later in the spring and that the temperatures were too warm to trigger the code again. So I definitely think it was fixed for a while.

Personally I am leading towards corrosion either at the sensor connection or at the ground straps. Another thought is that it might have something to do with the ambient temperature sensor being faulty causing the DME to freak out. That is just a guess though, I am not positive if the DME looks at it for cooling purposes.

I will probably start by cleaning the contacts for the coolant temp sensor with QD contact cleaner. May even swap out the coolant temp sensor again. Then probably will change MHD maps and check my ground strap (replaced already but probably should have put dielectric all over the connection).