Heater lukewarm
 

I have an X5 E53 4.8is. The heater only produces lukewarm air no matter what temperature I set the climate control on and no matter what position I have the knurled knob on (3 red dots etc). I purchased a Foxwell NT510 scanner and scanned the car. There were two faults (DME) that came up. One said:
2EF4/not present DME: Map thermostat mechanism
Also "map thermostat not active"
I also used the scanner to check the coolant temperature. The car had been driven for 30km and the temperature gauge was at the mid point of the range.
Scanner showed:
coolant temperature engine: 206 Fahrenheit
coolant temperature, radiator outlet: 133 Fahrenheit
I also scanned the engine using the OBDII mode. It threw up one error:
P0128/$12
coolant thermostat (coolant temperature below thermostat regulating temperature)
Before I fork out the $270 AUD for a new thermostat I thought I would run the problem past you people.
Any suggestions?

I had a P0128 code. My x5 also took a long time to warm up, had a lower engine temp on freeway, and higher temp when in stop & go traffic. All of the above were symptoms of a thermostat stuck open.

I replaced the thermostat, belts, water pump, and tank and all is good.

Thanks for that. Would not like to replace parts unnecessarily. Looking ahead to the likelihood of having to replace the thermostat I consulted my copy of Bentley only to find that there is little detail (or pictures) of the process of replacing the thermostat in the E53 4.8is. I have done a fairly thorough search of YouTube and can't find a relevant video. Does anyone out there know where I can find the relevant information?

Broken thermostat housing?
 

In order to fix poor heater performance (luke warm) I decided to replace the thermostat. Before putting in the new thermostat I checked the housing. Attached (hopefully) is a picture of what I noticed inside the housing. There seems to be a jagged edge as though some metal has broken away. Could anybody comment on whether this is just a result of the casting process or whether some part of the housing ha indeed broken away. Perhaps someone more knowledgeable than I could also comment as to whether this anomaly could be the cause of my heating problem. The old thermostat that I took out looked all right. I was hoping that it was jammed open but no such luck.