jag-miller, first off, welcome to JaguarForum.com. I think you will find a lot of useful information here and tons of people to help you out. But, we are a little quirky and like to get to know the people we are chatting with. So, please, stop by and tell us a little bit about yourself in the "New Member" forum. You will find out who are the movers and shakers around here.

Now, for your problem. From what you are describing, it is sounding like you are having wiring issues with the temp sensor wiring and this is resulting in an erroneous indication. But, this is not to say that it isn't actually overheating.

The first check I would tell you to do is to start the car and turn on the A/C to the coldest temp you can set it to and the fan on the fastest speed it will go. Now, with the engine running, open the hood and see how much air the fans are pushing. If you lean in over the engine compartment a little bit, you should feel quite a breeze coming over your face. If you are just getting a slight breeze or no breeze at all, then odds are you are suffering from a failed fan controller (common issue with the X-Type).

Next, you will need to locate the engine coolant temp sensor and undo the electrical plug. Now using a potentiometer (0-500 or 0-1000 ohm), you will need to add some wires and stick them into the plug to simulate some engine temps. First set the potentiometer to 100 ohms. This should bring it to the C mark (just off of the bottom peg). Next if you set it to about 260 ohms, it will be up near the H mark. You can then set the potentiometer to varying resistances and after a few seconds, it will read the corresponding temp. The big thing that you will want to do is to try moving the wiring a little bit and see if that causes the temp to shoot up. If so, then that confirms a wiring problem. It is possible that you have a high resistance in the wiring and it is leading to the false indications. Unfortunately, if this is the case, the only solution is replacement of the wiring for that sensor.

 

Sorry, can't help you with your problem, but I think I share your headache. Does the car do it on a long journey after 100 miles or so? And does the amber light come on telling you cruise isn't available a mile or so before it thinks it's overheating? Please let me know if you find an answer and I'll share with you if I find out somewhere else.

 

What is the age and condition of the battery? These vehicles require correct voltage at all times, so if you check battery voltage prior to starting the vehicle after several hours, it should be at least 12.5 volts. Anything lower can cause problems.

If there is any doubt about the battery it is best to replace it as a failing or weak battery can cause random DTCs and the MIL to come on.