Overheating in a 2009 XJ VDP??

During a 30’ drive, all of a sudden I got the dreaded red light illuminate and immediately noticed the temperature gauge needle was almost pinned to the top! I cautiously drove the car home (with several stops). Upon opening the hood, there were no signs of overheating, other than both fans were operating. A check next morning revealed a normal coolant level and no coolant leaks. Over the next few days, I drove the car several times, for up to 20’ or so, with no overheating warnings. Finally on one of the outings, I got the red light and temp needle all but pinned to the top!. Since that time, the problem hasn’t returned. My mechanic is reluctant to do any work until the problem becomes more frequent. During the time when the temp was extremely high (?), the needle would occasionally drop down to the 3/4 mark, only to return to the top shortly after! Under normal conditions, the temp needle is absolutely steady at the 1/2 mark. Any thoughts or similar experiences? Thermostat? Sensor? ECM?
Thanks … Bob

I would have the fault codes read, first, and go from there.

Thanks for your reply, Graham. Are you certain that fault codes are generated by overheating? I looked at a list of issues that would generate a fault code and overheating was not one of them?

No, but at least you will be sure that the fault is not with the ECU or one of the system sensors, for e.g.P1116 or P1117: Engine coolant temperature sensor out of range…

Thanks, Graham. That certainly is an option and I’ll have my mechanic check for any fault codes. I believe there are 2 temperature sensors, one near the thermostat, but I don’t know exactly where the other one is. Thanks for your help, Graham.

I’ll have my mechanic check for any fault codes

If your mechanic doesn’t automatically check for fault codes, it’s time to find another one.

No fault codes were recorded,