Map cooling
 

I got an error message on GT1 related to map cooling and it points out to the heating element in the thermostat. Although it looks like a removable piece for some reason I don't find it in realoem by itself. Any idea? Following the GT1 instructions I supposed to have 10.2 ohms impedance but mine does not. Even though the thermostat is good I do I have to replace it because the heating element?
RealOEM.com * BMW E53 X5 4.4i Waterpump - Thermostat

http://realoem.com/bmw/showphoto.do?id=11531436386

Yea my 4.8is had a failed sensor in the thermostat. Thermostat was fine, but GT1 said stuck open. I had to do it at that point.

It'll continue to function just fine as a mechanical-only thermostat until you get around to messing with it. If the dash indication annoys you then unplug the heating element and plug a suitable resistor in the connector so system thinks it's all good.

Otherwise all the heater is for is to provide override of the mechanical thermostat under certain conditions.

Rant on: One of the conditions is under continuous load. For example, when I pull a long grade in 5th, I can watch the coolant temp (on unlocked dash display) drop by 10 degrees, only to pop back up to the ridiculous 225 deg F under normal conditions. The (IMO only) excessive operating temp which helps them accommodate the extended oil change intervals, and to help meet emissions, etc. using an engine management system that still relies on cumulative fuel trims under open loop vs. a wide-band oxy sensor feedback system to control operation at all speeds and conditions (the ME 7.2 most certainly does not) and so forth. Well anyway, these operating temps then required quite a few band-aids to be employed as a result. One of the band-aids is to use this heater-system to bring the temps down under load since the higher cyl wall temps that accompany high running temps makes pump fuel more susceptible to detonation - thus this engine also has FOUR knock sensors. And knock sensors, unlike general engine management components, are not proactive in engine operation - they are reactive. Ok, so the whole feedback system is reactive to some extent -but still, lots of knock sensors isn't an advance when you realize they are there to react to conditions the engine management system cannot compensate for on a proactive control basis. Annoys the hell out of me, that's all.

OK, rant off. I still like my X, but fer cryin' out loud, BMW - really????

I don't have a light or message on the dash. I was trying to debug a starting problem that I have for about a year now and using the GT1 pointed me to the first DME problem which is the map cooling. I can live with the error in the GT1 but I was wondering if this can be the cause of the starting issue I have. I was reading somewhere that the map cooling system is used by the DME to set the proper air/gas mixture using the dual temperature sensor which is my case I believe is working although I had two values on pin 1-2 and 3-4. I might be wrong but I expected using the multimeter the impedance should be the same if the thermistors are the same at the same temperature.

If I recall the dual temp sensors may be slightly different. Or not. Damn this old age stuff. (I have a chart of resistance vs. temps somewhere).

Doesn't matter. You are correct, the engine management system uses current coolant temp in deciding various operating parameters. The biggies are the engine temp, and the mass air sensor voltage off pin #5 of the MAF. Other factors are involved, but in the ME 7.2, it'll run open loop until certain temps and oxy sensors, etc. come online. That means it's operating off of a learned table (base table from original modified over time by fuel trims determined during closed loop operation). As long as engine temp and mass air voltage is within a reasonable parameter, then by reference to its internal tables it'll have the fuel mixture (timing and duration of injector pulses), throttle idle position, ignition timing, and cam timing about where it needs to be. And no, that's not all there is being monitored even at cold start up - but those are the factors that place the initial parameters on the operating tables.

Engines are most sensitive to changes at idle and just above. That's why a MAF curve is steep at the lower end and flattens out. Higher resolution at low loads. Dunno about the starting issue as so many things can conspire to affect low speed running which may have no discernible effect at higher loads.

civdiv, you know this car inside-out. The starting issue, I guess is related to temperature of something somehow. The engine starts perfect in the morning but if I stop the engine and try to start it in a couple of hours for some reason cracks a few time before it starts and it seems like a few cylinders start but some of them just don't until I accelerate and then it's all good. It feels like it's a misfire or the not enough gas. I know the fuel pressure is ok but I suspect something with what the ecu reads from some sensors.
I ended up checking the thermostat heater because the GT1 pointed me in the direction but sure it could be one of the sensors in the dual temperature sensor.
If you know what I should check I can connect the GT1 and read all the parameters. Unfortunately some of them don't have much meaning.

Lemme ponder..............

This is a good explanation but not good enough for me to identify the sensor that might cause the problem.
http://www.meeknet.co.uk/e38/e38_map_thermostat.pdf

How much is the stat for your engine anyway?

The thermostat is about $100 online. I just replaced it a couple of years back with the water pump. After I put so much effort in the transmission rebuilt which was not a success I just don't like touching it anymore even though i do. I am not looking forward to replace the thermostat. As civdiv was saying the heater in the thermostat shouldn't be the cause of my starting problem but maybe one of the sensors.
I just measured the impedance of the dual temperature sensor and the values are different. I expected them to be the same. I found the table in the GT1 for the impedance / temperature. Shouldn't be both values the same?