[ForTheD]

So I had the SES light pop on a few weeks ago, check it, P0128 (Coolant Thermostat Malfunction), erase it.
It comes back about 6 days later.
The car is acting just as normal including the heater and the engine response.
I have owned this car for the last 6k miles, and the temp always takes about 10 to 15 minutes to get to 220 or so, and there seems to be no change there.

Searching around I did not find a concrete fix for it, other then a the one person I saw replace the thermostat. This seems a bit extreme so I wanted to see what you all thought.

Is there a separate sensor somewhere?

p.s. I'm not taking it to the dealership. out of warranty and I like doing this stuff my self (with the help of the forum of course.

Thanks everyone.

[ENINTY]

Originally Posted by ForTheD

So I had the SES light pop on a few weeks ago, check it, P0128 (Coolant Thermostat Malfunction), erase it.
It comes back about 6 days later.
The car is acting just as normal including the heater and the engine response.
I have owned this car for the last 6k miles, and the temp always takes about 10 to 15 minutes to get to 220 or so, and there seems to be no change there.

Searching around I did not find a concrete fix for it, other then a the one person I saw replace the thermostat. This seems a bit extreme so I wanted to see what you all thought.

Is there a separate sensor somewhere?

p.s. I'm not taking it to the dealership. out of warranty and I like doing this stuff my self (with the help of the forum of course.

Thanks everyone.

It's most likely the heating element in the thermostat not functioning properly. The thermostat is electronically controlled and has a heating element in it (not really sure of the function it performs). My car has the same problem, which cropped up last winter. I kept clearing the code until the Spring came hoping it would correct itself. All summer the code did not reappear, but in November, when it got cold again, the code is back. Changing out the T-stat is the only fix.

The good news is the T-stat has been redesigned, so hopefully BMW has addressed the problem. Second, the T-stat is designed to fail "open" so if it stops functioning it will not stay close and overheat the engine.

[fdriller9]

I cant remember which chassis this pertains to, e46 or e90, but a common problem is that the thermostat gets stuck open. Symptoms are that the car takes forever to warm up (because the pump is constantly running, sometimes at full speed).

I would have the thermostat replaced for peace of mind.

[ForTheD]

Thanks guys. I'll just keep an eye on it, and replace the pump come spring.

[MrDummy]

Im getting mine swapped out via cpo warranty

[MrDummy]

Does anyone know if they do swap thermostat that they will swap water pump as well?

Or will they only do what the code says to do? I have cpo but it would be nice to have them swap it out at the same time.

[ENINTY]

Originally Posted by MrDummy

Does anyone know if they do swap thermostat that they will swap water pump as well?

Or will they only do what the code says to do? I have cpo but it would be nice to have them swap it out at the same time.

I doubt they would unless the pump is broken.

[MrDummy]

^^ Thanks they said my P0128 has a TSB on it and all they had to do was reprogram computer, but still want to charge me my $50 copay for CPO, i need to find out if this is legal..

[whip_lash]

So the CPO warranty will cover this error code? I called my dealer up and they want to charge me for diagnosing the problem, they said it will take 1-2 hours which is insane it took me 2 secs!! they also want to charge me for that and plus the $50 deductable if its covered under warranty... this CPO warranty is total BS.. unless you run into a major problem.

[whip_lash]

I dont know how you guys got this covered under the CPO but i just went to my dealer and they wont cover the thermostat under the CPO... so pissed!!

[ENINTY]

Originally Posted by whip_lash

I dont know how you guys got this covered under the CPO but i just went to my dealer and they wont cover the thermostat under the CPO... so pissed!!

Not sure what that code translates to in the BMW code format, but I think you could make an argument that it is an emissons related failure (why else would it show up as a P code in the OBD 2) and should be repaired under the separate U.S. mandated emissions warranty.

[whip_lash]

I just got the car back from the dealer (was doing HPFP and injector recall) but when i got it back the code was gone. I guess they re flashed the computer or something... w.e it is its gone!

[fl0wmastr]

The thermostat is the #1 reason, but I also got this code when I didn't mix the coolant/water mixture right.
Too much water raises your freezing point and too much coolant lowers the flow rate of the fluid and triggers the code.
The slower fluid doesn't cool the engine as well. If you've already replaced the thermostat, I'd try flushing the coolant in the system.
When I flushed my system the code went away and never came back.

If that doesn't fix it, I'd replace the thermostat, coolant temp sensor, the water pump, and the expansion tank. Unless you know these have been replaced recently.

[ForTheD]

Originally Posted by fl0wmastr

The thermostat is the #1 reason, but I also got this code when I didn't mix the coolant/water mixture right.
Too much water raises your freezing point and too much coolant lowers the flow rate of the fluid and triggers the code.
The slower fluid doesn't cool the engine as well. If you've already replaced the thermostat, I'd try flushing the coolant in the system.
When I flushed my system the code went away and never came back.

If that doesn't fix it, I'd replace the thermostat, coolant temp sensor, the water pump, and the expansion tank. Unless you know these have been replaced recently.

I just got the message that some one replied and I realized I never reported back. I changed the thermostat probably about 4/2011 and have not had the error since. I wish I would have thought of coolant flush first though, that would have been helpful for the forum to know.

[saeng]

bump to an old thread.

i also have a P0128 code. i just replace the Thermostat and cleared the codes but the p0128 keep coming back. anyone know what it could be?

[jb10]

Originally Posted by saeng

bump to an old thread.

i also have a P0128 code. i just replace the Thermostat and cleared the codes but the p0128 keep coming back. anyone know what it could be?

i'm having this same issue. replaced the thermostat and the coolant sensor and it keeps coming back. how did you get your issue resolved?

[GoRomeo]

Originally Posted by saeng

bump to an old thread.

i also have a P0128 code. i just replace the Thermostat and cleared the codes but the p0128 keep coming back. anyone know what it could be?

Originally Posted by jb10

i'm having this same issue. replaced the thermostat and the coolant sensor and it keeps coming back. how did you get your issue resolved?

I had this code few years ago and its due to an "stuck open thermostat" but I was able to cleared it with the Torque app. Now you wait until your water pump goes bad which is unfortunately not very long and replace both.