Need help troubleshooting thermostat error

Hey Guys,
New M3 owner here. When I took the car in for the pre-sale inspection, the DME threw (105) 69 Engine Temperature Signal Implausible (1x; Not
Present). I was told by the tech there that the thermostat needs to be replaced.
I took possession of the car today and even after driving 30 miles on the freeway, the temperature gauge needle stayed pegged in the middle. No sign of over-heating, is that possible with a stat failure
What do you guys think could be the problem? Any ideas on troubleshooting this?

Seems like it would be the actual temp sensor.

As stated in the other forum;

The thermostat is designed to fail open. Not like domestic vehicles that fail closed. Your thermostat probably isn't the issue. There are 2 temp sensors that might be causing the issue. Check the connectors. Your error means it sees the temp as completely out of range when compared to the rest of the data that it's processing.

Where are these sensors located?

Check out menu 7 after unlocking OBC.

SolidJake has a great thread where everyone is checking in with their engine temp.
*Edit I couldnt find that thread.

My operating temp with new cooling system hangs around
88-95°C


Your tstat sounds like its broken open.

A pic of my old t stat.

I got a chance to get into the OBC menu and take the car for a closed circuit test. This is what I found.

External temp: 75F

First leg: 15 miles with AC ON
Freeway, constant 80 mph, 3k rpm
Coolant temp: started from 80C(the engine was already warm when starting) and reached a constant 86C(needle at 12 o'clock)

Second leg: 15 miles with AC OFF
Freeway, constant 75 mph, 3k rpm
Coolant temp: went from 86C to constant 83C

Third leg: 6 miles with AC OFF
Semi-surface street, constant 60 mph
Coolant temp: went from 83C to constant 80C(needle a minute or two to the left of 12 o'clock)

What do you guys make of this temp range? Do you think my engine is running cold? Is yes, it does look like its the stat does'nt it.

Yep seems a bit cool.

Temps all seem good to me. With a/c on they should go up and mine usually always runs dead center but tstat seems to be working if it changes temps up and down. Try running it with heater full blast and record numbers

I thought I read somewhere on here about there being a DME update on engine running temps.

2 mile drive from work, heater at full blast, external temp 65F, coolant temp max was 83C
Also looking at this thread it looks like my cooling system is OK
http://www.e46fanatics.com/forum/sho...d.php?t=912749

Can I just clear the error code and forget about it? Do you guys know how to DIY clear the error?
Thanks for all your input.

Originally Posted by 40mikemike

2 mile drive from work, heater at full blast, external temp 65F, coolant temp max was 83C
Also looking at this thread it looks like my cooling system is OK
http://www.e46fanatics.com/forum/sho...d.php?t=912749

Can I just clear the error code and forget about it? Do you guys know how to DIY clear the error?
Thanks for all your input.

I just looked over thread again. Doesnt seem like sensor cuz your temp guage is so near normal and dont think tstat cause car prob wouldnt get to normal temp on guage if open tstat.Should be able to use just about any obd2 scan tool to erase. Try take car for a good drive before you think its good for sure. Keep it revved around 4000 rpm in first or second so it doesnt get much wind( disconnect fan) see that tstat is opening or if it gets too hot. Could use laser temp gun on rad. Just some more tests if you want. Sounds good to me but just watch the guage and erase is prob good

Im getting a bluetooth OBD2 scanner so I can keep an eye on the vitals. Will continue monitoring and report back.
Thanks BC and all.