This is the 2nd time this has occurred, first time was about 3 years ago it is a very odd occurrence.

Driving on the highway normal coolant temps reading via OBD2 (86C) , suddenly I get Engine High Temperature warning,
shortly after I get Engine Overheating warning and also notice my A/C is no longer blowing cold.
I pull over immediately and hear the fans kicking on high however the whole time my OBD2 temperature gage
reads normal temperatures in fact quite cool. and my coolant reservoir is full, no leaks. once I turned the car
back on immediately after all is back to normal AC working again etc.

Anyone else encounter this? I'm stumped

 

Given coolant level is correct then could be a suspect ECT (Engine Coolant Temperature) Sensor. An incorrect output to the ECM is likely to trigger those events.

Graham

 

Thanks for the reply,

does the ECM get its coolant temperatures from a different
sensor than the obd2?

About 2 years ago, I changed the coolant pipe at the rear of the engine. This pipe does contain a temperature sensor
which was a darker color than original.
I'm wondering if the ECM gets it data from one sensor
and obd2 from another.

An even scarier thought, could the ECM be getting its
Temperature from the engine block which is actually
Overheating due to a malfunctioning thermostat?

 

OBD2 is fundamentally an output device

just order one of these and change it already!

https://www.ebay.com/itm/For-2012-20...wAAOSwecJddfvA

 

Just found out there are 2 of these sensors, one is installed in the coolant pipe at the rear of engine
and one at the front of the engine on a coolant pipe before coolant enters the engine.

 

If the coolant level is low to the point of the sensor not touching the coolant, or if there is air in the system, the sensor will not show an Overheat condition.
Just a possibility.

 

can put that worry to rest i think; this is not possible on any car i know of. ODBII is an information system standard for how to talk to the ICE with an external device; the pinout, the communication protocol, transfer rates, which codes are which (except for manufacturer-specific extensions, of course) and so on.

an OBD port isn't wired directly to the ECM plus one or more other sensors X, Y and Z, it's wired to the entire car's brain, typically called the integrated control electronics unit but maybe jaguar has another name. in some cars that brain can even drive multiple ECMs if for some reason those ECMs have different concerns, like in a hybrid.