Increased Emissions Error Message

[rangerb3]

I have been getting this message on my multi-function display for the last few weeks. I thought it was from accidentally putting regular unleaded into the fuel tank...but, I now know that this is not what's going on....

I recently bought a generic OBDII code reader and was able to pull up the DTC's using the new scanner. What's coming up is a PO128 which references the thermostat saying that the thermostat is not regulating the temperature properly. I have cleared the DTC at least 3 times and it keeps coming back. The service manual shows a temperature switch on the thermostat and one on the water pump housings...it looks like one senses the supply water temp and the other the return water temp....

Any ideas before turning to the dealer for help?

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Best Regards,
Rangerb3
E63-'05 645Ci

[Ivan213]

I have been getting the same code and have read it could be -
Low engine coolant level
Leaking or stuck open thermostat
Faulty cooling fan (running too much)
Faulty coolant temperature (ECT) sensor
Faulty intake air temperature (IAT) sensor
I will actually try to do this next week and will most likely change the thermostat which most people have done and fixed the problem. If you do get it fixed before I attempt I would like to know what your fix was

[rangerb3]

I took it to the dealer today and they said it was a stuck thermostat. They also said the lower radiator hose was leaking and graciously offered to change both for only $850 bucks! I'm very mechanically inclined but never worked on a bmw...Maybe for that price, I should give it an attempt..... Strange that it would be another thermostat since the current one was changed out in Feb 2009....

[bpdover]

It is up to you if you want to pay the 850 to the dealer, but that is a $60 the termostat is a $60 dollar part that takes about 10-20 minutes to change, there are only 3 bolts holding it to the water pump. you just un-click the pipe, change the thermostat and reset the error.

[Ivan213]

I would never pay $850 for that job. Most definitely change it yourself and save $750

[Cunsuelo]

The lower radiator hose leak is likely just the radiator outlet temp sensor o ring. A .50 cent fix.

[Iceman44]

It is up to you if you want to pay the 850 to the dealer, but that is a $60 the termostat is a $60 dollar part that takes about 10-20 minutes to change, there are only 3 bolts holding it to the water pump. you just un-click the pipe, change the thermostat and reset the error.

How about this...just had the job done at the dealer in Houston on my '03 745 and the part (thermostat) cost $94.65 (dealer charge) and $39.45 for the coolant as the bled the system and cleared the memory ($134.10 in parts) and 2.5 hours of labor @ $142.50 per hour. I paid $491 for the job and the car is running great (emission Fault error cleared and check engine light is now off).

[BMW735i87]

On my 2008 E63, I was just quoted $1,360 for this exact same thing... Unreal.

[jclausen]

Replace the map thermostat that is what controls the temperature