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The Story.
Battery went flat with car sitting so was removed for chargeing. Then I went on a 40 mile freeway journey. At about 75mph check engine light came on with the RED warning light. I checked gauges and temperature gauge was at absolute maximum. I ran heater full and pulled over. The cat was running smooth and the engine did not feel excessively hot. I turned her off and waited for her to cool. When cool I checked fluids and engine oil and coolant were normal. When I restarted car and drove home temperature gauge read normal and after a while the check engine light went out. Two OBD codes in memory were Po116 coolant temp circuit, and P1111 pending system pass.
I cleared codes and so far no problem. Might this be a computer glitch caused by powering down sytem?
like others said.. a battery with a low voltage will throw some crazy things at you. I've learned once you jump a battery or let a battery go flat it's never the same again..
Only other thing I can think of is the radiator being clogged with junk.. if you have access to an air hose you can blow out stuff from the radiator grill.. I had a Nissan truck that the temp. guage spiked randomly because it was hot.. but like you said the temp was normal but it could have cause a hot spot near the sensor.. *shrugs*
I would definitely look into this one. I believe the sensor in question is part of the whole plastic thermostat housing and pipes, front and center, on top of the belt on the 4.2 engine, so very easily accessible. It is light grey in the picture below. I would re-check the harness connector, and make sure it is clicked in place. Also, try and follow the wire and check for any type of damage. The computer is complaining about the circuit itself (either short of completely open).
Separately, this whole plastic assembly, thermostat and sensor included, is available from Jaguar for a not-too-exorbitant price, and pre-assembled. I replaced mine shortly after I acquired the car as I figured 13 year old plastic had its best days behind it. Furthermore, if any of this fails, you are stranded. It does not really require you to drain the whole cooling fluid, just a bit off the top. There are several posts detailing the procedure, including these dreaded rear pipe bolts. Looks something like this:
Removing the battery to charge should not result in the temp. gauge going to max and check engine light. To me it's most likely a malfunction of the temp. sensor.
If you follow fmertz advice and replace the pipe assembly you will likely solve the problem.
Thanks All. The battery is on its way out so I replaced today with the best I could get locally, a Maxx EverStart H8 1000/900 from Walmart. The thermostat housing has the "bolt" issue so I'll replace that and do a flush. Thanks.
Measure at the bare metal at the front of the head. It will be hotter than the water temperature by 10 degrees or so but provides a much better target than the small metal part of the temperature sensor itself. It should read in the 210 F range at full operating temperature.
I have had sensors, even brand new ones, provide an incorrect resistance signal to the ECM as displayed on an IR gauge. After replacing the cross over pipe during a cooling system rebuild the fans ran all the time even in single digit temperatures. It took two changes of the sensor before I found one that stopped that.
It should be noted that the sensor resistance is also subject to additional ohms between the spade connector and the ECM.
Phantom Overheating?
