Hi all,

A bit perplexed here.
I noticed that the coolant temperature, given by the OBD reader, is at -40°C when read from the engine module.

However, the dashboard gauge is always fine (it's not the RealGauge thing though, so it's just quickly getting from bottom to middle and just stays there), and the same item read from the transmission module (which, for some reason, gives the engine coolant temp), seems ok as well : about 87°C.
I did notice that the long term fuel trims are around +2.5%, (last reset was about 2500 km ago), and the short term trims were oscillating between +3 and +6% when I checked (after a relatively long ride so engine was at normal operating temperature). External temp was around 7°C. All the O2 sensors are fine.

I'm not sure what to make of this, or even if these elements are related at all. Temperature sensor issue, engine module issue (yikes), or just no issue at all ?

This part is really inexpensive so I'm thinking I could just change it and see how it goes, but if possible I'd like to get some certainty.

 

There may be 2 sensors. Regardless, until it reads the right temp it can't fuel or run properly.

 

There is only one Coolant Temp Sensor (CTS). It sends the signal to the engine ECU and the engine ECU also sends it to the transmission module (TCU) and to the Instrument Panel. Since you can read the temperature via the TCU, and the temp gauge works, there is no issue with the sensor (bad CTS would cause the engine to run like crap). It is possible that your scanner is not fully compatible with the type of data coming from the ECU so it cannot display the engine temp info coming from it. I would first try with another scanner.

 

my xk did the same I was out of town when I noticed the temperature just flashed on the dashboard very quickly went away I drove 400 miles no problems the next day I went to work nothing on my way home I parked in front of the house and the car over heated I had no leaks my fans were working so I took it to my mechanic and he sed that the thermostat housing was cracked it’s cheep plastic so got it replaced and thermostat and water pump too that way I didn’t have any problems I get in my car and go with no problems good luck

 

I'll assume M. Stojanovic's answer is the correct one, as it is by far the less scary

I've read a bit about fuel trims and as I understand, a positive 2.5% is still normal.