Hello All - for my 2007 XK..

My engine light has been intermittently illuminating, and when I connect my scanner to the port and read the code it displays the following:

Current DTC
P0128 1/1
Coolant Thermostat
(Coolant temperature below thermostat regulating temperature)

Car drives fine and I can clear the code and then a few days later it pops up. I don't observe any coolant/radiator issues when I inspect the engine bay when the engine is running.
Any ideas what I should look? Bad sensor? Good sensor? Nuisance? Any advice appreciated.

Thanks
Reg

 

You need to replace your thermostat.
But follow the advice of post #18 in this thread:
https://www.jaguarforums.com/forum/x...9/#post2003750
and replace the housing as well, since you’ve already taken it off.
Replaced mine a few years ago, same code.

 

Thanks so much for providing that thread detailing the issue. Will get it addressed.

thanks,
Reg

 

Thermostat is stuck open - problem shows up in winter on mine - I just clear the code - one day I'll replaced the thing.

 

It is quite a bear to replace.