I have a strange problem. When it is really cold (-28C) when I start the car the Engine Overtemp Light on the dash comes on and the temp gauge does not move at all. The first time it happened we fiddled with the plug on the sensor and after 2 tries starting it, the condition cleared up. It worked for about 2 days and then it happened again Monday morning. I brought it in again and the sensor was replaced. This morning another frosty morning and it happened again.
The circuit is pretty simple, the sensor has 2 wires and one connects back to the ECU. Not sure why the other wire gets bridged to the MAF Sensor and the THR Sensor as the ECT is just varies its resistance based on temperature.
This is on a 2008 Super V8 with about 150k Km on it. No history of this problem prior to last week.
Thanks in advance for any suggestions.
Rick

 

Have you checked your coolant strength?

If you are running 50/50 you are almost at the freeze point of -34*C.

If coolant does not flow, then you will see overheat right near the sensor.

Every time they bring it indoors, doing almost anything will fix it because the
coolant warms up ... presto fixed.

Try 60/40 which can only happen by starting with concentrate. The 50/50 premix
won't work because it can never be stronger than 50/50.

see chart here:

http://hellafunctional.com/?p=629

 

It never gets that cold here in the Northeast - I personally use a 70/30 mix in all my vehicles.

Full strength and Distilled water to get to the proper ratio..

 

Once I have this condition the car operates normally, it heats up and gives heat in the cabin. The only abnormal thing is the auto climate control blasts cold air on me until it warms up and I noticed the cooling fans come on high initially. The Overtemp light stays on and temperature gauge never moves.
Do you think that error light latches and doesn't reset even when there is normal coolant temp from running?

I did ask the mechanic to check the coolant strength and they said yup it went up right up. I'll ask what temp it was good to, around here we pretty much add antifreeze until it goes off the scale cause chances are it will get that cold.

Also, I had the block heater plugged in for about 2.5 hours before starting.

 

Hey there rickpwilson. Being from the peg as well, I can tell you that antifreeze shouldn't be a problem as I run about 50/50 in my STR and never have a problem. I'd say its more likely a electrical issue or bad part.
Also, is that the 08 Super V8 that our Jag dealer had here? The silver/black one with 150K? I was looking at getting that myself but after looking into it more, I walked away due to all the possible issues it may have. Not to scare you, but there were just too many red flags with that car. Accident history, cracked rear rim, already replaced rear control arms from a high speed impact or something. I know those guys there pretty well and they even told me if they had known all the issues with the car they never would have taken it on trade. There is a reason they dropped the price so much!
I hope that everything works out with it though. It is an amazing car when its all working right! And this forum is a great place to start.

 

So that high temp light does get latched but as soon as it gets reset and the car is in the garage it works fine. The code it is throwing is P0116 Coolant temperature signal sent to the Engine Control Module (ECM) is not within specified range.

 

After about 3 hours I restarted the car, outside temp was -21c and no code.
Its morning, overnight temp was about -25 block heater plugged in all night.
Turned the key to on and after a few seconds the overtemp light came on. Started the car and let it run for about 1 minute.
Shut it off reset the P0116 code turned it back on and it threw the code again. I am letting it run to warm up and I'll reset the code again. Stay tuned.

After running for about 5 minutes until I got a little warm air out of the vents I shut down and checked for the code and it wasn't there. I restarted and after a minute the code came up. I reset the code and the temperature gauge registered and the light went off. I think I'll increase the ratio of antifreeze as a first step.

 

Overnight temp was about -25, block heater plugged in all night, when I started it this morning it was -22. The High Temp check light came on immediately.
I connected the ODB reader and reset the P0016. The light went out, the temp gauge deflected a bit and all was good from this point on.
So it appears it only fails after the car sits for an extended time in the cold and on initial start up.

Maybe I just need to move to Florida.

 

Faulty sensor, ground or sensor connector.

 

I am not so sure it is temp related. I had the same problem a couple of months ago.
Morning start up, temp warning light on, no gauge readings, temps in the lower 50's F. I popped the hood and everything looked nominal including coolant level in overflow tank. Drove about 5 miles and the gauge never moved, pulled over popped the hood or should I say bonnet again and everything looked normal, engine was not over heating so I turned around and went back home. At home I checked and had a U0116 code, I cleared it and everything came back to normal and knock on wood the problem has not come back-(yet)

 

So one thing I forgot to mention was while they were diagnosing the check light they reported the battery was dead. That it was all covered in frost so we installed a new Interstate battery.
Jan 5, replaced battery
Jan 6, replaced ECT sensor
Jan 7, Diagnose, meter our wiring to ECT sensor.
Jan 10, I hooked up a ODB scanner which displayed live data. I turned the ignition on and I got the overtemp light immediately. I reset the check code and then started the car it ran normally.
I looked at the PID's and noticed that the ECU voltage was only at 11.5V with the key on but jumped up to 13v when the car was running.
I checked the battery and threw a charger on it, the little smart charger I put on indicated 25% charged.
Fearing there was a problem with the charger I attached another higher powered intelligent charger and it read LOW.
So I charged the battery on the small charger for over 14 hours and it would never get to 100% charged.
This morning the car started fine no check codes.
I brought it back to the shop and they contacted Interstate, the battery also doesn't have the vent hole in the battery which I assume is an important thing. They are going to replace the battery.
Stay tuned.....

 

Yes, the battery vent is important. Sounds like the shop installed an incompatible battery in your car that has issues.

When I purchased my S Type it had a "new" so I was told Interstate battery (same deal - no vent fitting) needless to say the battery was issue plagued.

I replaced it with a proper Bosch battery and zero issues since - almost 3 years now..

 

Monday the proper battery was fitted and it failed again yesterday morning.
The weather is going to warm up around here its only -11c this morning so we will see if it is in fact deep cold related.
I don't understand why it takes an extended period of time for the problem to happen. I can use the car all day long, leave it parked at work for 4 hours in -28c and it starts without the check code. So far this has only happened first thing in the morning and on very cold nights.

 

rickpwilson,

When you park the car for the night, attach your reader and check if you are getting code P0116 after driving for the day. Then clear any codes. The next morning, WITHOUT starting the car, check for codes again.

It might helpful for you to know exactly when does the ECM register the code in order to track down the likely fault. IOW, does sitting overnight in the cold induce the fault, or does starting the car on a cold morning record the fault.

Something else to consider is the fact that all the ground points are vulnerable to oxidation, and if I remember correctly the effects of an oxide layer on aluminum are exaggerated at low temperatures. Make sure that you clean the ground point for the ECM, and if the ECT Sensor grounds to something other than ECM grounds, make sure to clean that ground point as well.

 

Jan 14
The weather finally warmed up overnight low was only -15C. I had the car block heater plugged in all night. The problem recurred, P0116 as soon as the key is turned on.
ECT temp registered 26C due to being plugged in.
Ambient Temp -11C
I reset the code and the car started with no further codes. Went to work the car sat for 4 hours and then again for about 6 hours without throwing the code on start.
The problem seems to related to sitting for an extended period of time.
Checked the coolant level and all was good.
My mechanic put his reader on the car at the end of the day and pulled additional codes.
B2139 Data mismatch between PCM and PATS/instrument cluster
B1875 Turn signal / Hazard power feed circuit failure
Going to the Jag Dealer today to see if they can shed some light on this.

 

Whoever is installing your batteries is failing to do the most important
thing for performance and longevity.

A full charge using a trickle charge on the bench without any other
connections. Batteries are normally shipped at less than full charge.
On the H8/Group 49 battery you are probably using this trickle
charge can take up to 48 hours or more depending on your charger.
The last absorbtion charge stage will be at very low current and
takes a lot of time.

It is then the alternator's job to top off the battery to compensate
for the current used to start the car.

Make sure you have a H8/Group 49 battery and not the Group 93
that Interstate dealers like to fob off on Jaguar applications. If not,
go get a H8 from Walmart, made by Johnson Controls.

The venting provision is critical for safety, as well as promoting
a rustfree trunk interior.

Additionally, check for high current draw when the car is off and
has gone to sleep. It is specified at 30ma for the X308, and should
not be much higher on the X350. It will take 30 minutes or more for
the car to go to sleep.

 

Because the battery is retaining enough charge during the day
to avoid your low voltage problems. Overnight, the charge drops
below the critical voltage.

Overnight, your engine is also colder, consumes more amps during
start, and immediately thereafter the battery is at a lower voltage
until it has time to recover the charge.

 

January 15th and it didn't fail this morning. I was all set to try and capture a trace with the odb reader as close to the time that it fails as possible. The ambient temp was -11C and the ECT temp was +5C.
I spoke with the Jaguar Mechanic and he suggested I check the thermostat and that perhaps the code was getting set after I shut it off rather than before I turned it back on.
I also took PLUMS advice and hooked up the battery charger last night. My little Smart charger indicated the battery was between 50% and 75% charged.

 

Since you have several vehicles, see if you can leave the XJ block heater and charger
plugged in all weekend.

It takes those smart chargers a looooong time to do the final charge. And it will
take longer when you have the battery hooked up to the vehicle.

Full charge resting voltage on the battery chemistry you have is between 12.7 and 12.8
volts measured across the terminals after disconnecting the charger for at least an hour.
Overnight, without charging you should see 12.65 volts or more when you first approach
the car and have done nothing else.

You will not be in the final absorbtion phase until the charger shows less than a half
amp of charging current, preferably .1 amp.

That final absorbtion phase is what gives your battery staying power.

From the sounds of things, your codes are being set because of sagging voltage
immediately after starting due to starter current draw. Having the reserve of a
fully charged battery might make those symptoms go away. Well worth trying
the over the weekend charge before proceeding with further diagnostics other
than perhaps excessive idle current draw.

 

This morning, -17C and the little smart charger showed 100% charged after being plugged in for 12 hours. I didn't plug in the block heater last night so the ECT Sensor read -12C.
Hooked up the ODB turned on the key and no over-temp light!
That is 2 whole days in a row.
I am going to take PLUMS advice and park the Jag for the weekend and fully charge this battery.
Thanks to all who have replied this is a great forum.