engine temperature indication fault?
#1
#2
Mike, getting that warning normally means that the computer is looking for the engine temp sensor to be giving it a resistance that is relative to what the engine is at. In all cases, the temp sensor should have a resistance that is around 100 ohms at ambient temps (varies based on actual outside temp) and then will go up to 260 ohm (as I recall) for an overheat condition (around 250F). When the computer looks at the temp sensor and doesn't see the resistance in the 100-260 ohm range, it assumes there is a fault with the circuit and gives you that nice message. If you can get your hands on 2 different resistors (say a 100 ohm and a 250 ohm, 1/4 watt heat rating), you can unplug the temp sensor and bend the leads of the resistor to slip into the plug in place of the temp sensor. Then you can turn the car to the RUN position (don't start the engine) and you should see the temp gauge come just off of C with the 100 ohm resistor and then you can repeat it with the 250 ohm resistor and it should fall just short of the H on the temp gauge on the dash. If you can pass both of these checks, then your temp sensor in the block is bad. If you are still getting the error message with the resistors installed, then odds are you have a wiring issue where something has rubbed through the insulation (most likely) and is grounding out the signal, making the computer think that the sensor has failed to 0 ohms or there is a high resistance connection in one of the plugs.
If you want to tackle the electrical side of things, let me know. I'll do what I can to help.
If you want to tackle the electrical side of things, let me know. I'll do what I can to help.
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ExKayRick (02-05-2023)
#3
Thank you Thermo. After troubleshooting some possibilities I noticed my coolant was on the low side too.
This morning after 5 minutes of driving the warning went out so I'll start by topping off the coolant.
If the message pops up again I'll try your suggestion. I think you may be right though, the warnng sounds more like a sensor / electrical issue than actual overheating.
Thanks again
This morning after 5 minutes of driving the warning went out so I'll start by topping off the coolant.
If the message pops up again I'll try your suggestion. I think you may be right though, the warnng sounds more like a sensor / electrical issue than actual overheating.
Thanks again
#4
You can check the NTC thermistor-type coolant sensor yourself quite easily with an ohm-meter (usually part of a multimeter). Unplug the sensor connector -- this will reveal the pins inside the shroud, to connect the meter leads. When cold it should be high resistance, hot it should be low resistance. The ratio is quite large. Example, mine (S-typeD) reads 3K5 (3,500ohm) when hot, a lot more when cold. So measure it when hot, then look for a large rise in resistance as the engine cools. It could be there was an "iffy" connection before you unplugged it for testing due to subtle corrosion, and that's all it is. After all, it's considered a hostile environment with engine heat and vibration -- not much vibration with a Jaguar of course!
Unplugging and replugging a few times will clean the contacts enough to establish if the fault is there -- something you can do in seconds and for nothing while you're at it.*
Leedsman.
*Tutorial -- a small current of milliamps is passed through the thermistor by a 'pull-up' type resistor in the micro. from the +5volt supply usually. The analog voltage at the + side of the thermistor then varies according to the resistance of the thermistor, directly related to engine temperature. This analog voltage is converted to digital by an A/D converter, and the resultant 8-bit number is used by the micro. to assess engine temperature. 8-bits gives you 255 steps of adjustment. The micro then makes decisions from the that binary number: E.g. for cold cranking to start (low voltage, low number), the petrol mixture ratio is made very rich. The cold running ratio is made richer than normal to avoid misfires and acceleration flat spots. When engine is hot, the mixture is reverted to normal, around 15:1 stoichiometric, with idle enrichment and acceleration enrichment. A very different strategy is in operation for cold-running a diesel engine.
Unplugging and replugging a few times will clean the contacts enough to establish if the fault is there -- something you can do in seconds and for nothing while you're at it.*
Leedsman.
*Tutorial -- a small current of milliamps is passed through the thermistor by a 'pull-up' type resistor in the micro. from the +5volt supply usually. The analog voltage at the + side of the thermistor then varies according to the resistance of the thermistor, directly related to engine temperature. This analog voltage is converted to digital by an A/D converter, and the resultant 8-bit number is used by the micro. to assess engine temperature. 8-bits gives you 255 steps of adjustment. The micro then makes decisions from the that binary number: E.g. for cold cranking to start (low voltage, low number), the petrol mixture ratio is made very rich. The cold running ratio is made richer than normal to avoid misfires and acceleration flat spots. When engine is hot, the mixture is reverted to normal, around 15:1 stoichiometric, with idle enrichment and acceleration enrichment. A very different strategy is in operation for cold-running a diesel engine.
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ExKayRick (02-05-2023)
#5
Finding Temerature sensor
On my 2008 XKR, I had one incident where I got the fault message, but it went away after about 10 minutes. I would like to clean the sensor contacts, but not sure where it is. Anyone that can point me where to look will be greatly appreaciated. Of course a photo would be also nice.
I drove an XJS Coupe for 23 years and have updated to this wonderful car last year. Not too many issues so far. I do have an extended warranty, but this seemed like something I can handle.
Tx.
I drove an XJS Coupe for 23 years and have updated to this wonderful car last year. Not too many issues so far. I do have an extended warranty, but this seemed like something I can handle.
Tx.
#6
Hey Mike! Just checking to see if you got the fault code again after topping off the coolant? I just got the same code today. I haven't driven the jag much and so I thought I'd drive it alittle today before Eurotoys picks it up on Monday for some work and the fault code come up this morning. I did see my coolant level is lower than minimum. After 5 years of ownership I haven't added any coolant. LOL. You would think there would be a warning on the dash for low coolant. Funny thing is my Rover had an "Engine Coolant Low" with only 4,800 miles on the odo and the dealer said they have customers with the same thing as it's common on my Rover.
#7
Thermostat
Hey Ghostrider, Yes, I topped off and it went away but a couple of months later I was getting a CEL for a P0128 code. I found out that the thermostat on our models tend to get stuck open and are actually over cooling the engine. I guess their not careful when they install them at the factory and the gasket moves to a position that blocks the thermostat from closing.
I ended up buying a thermostat and gasket for like 17 bucks from Gaudin Jaguar. Replaced the old ones and problem solved.
Try just topping off first but if it comes back or you get a check engine light with a p0128 code, you might just want to replace the thernostat. It takes about 30 minutes labor and top up the coolant again (you lose some coolant removing the old thermostat). Mike at Eurotoys should be able to do it no sweat.
More info here: https://www.jaguarforums.com/forum/x...ing-cel-61749/
Hope this helps
I ended up buying a thermostat and gasket for like 17 bucks from Gaudin Jaguar. Replaced the old ones and problem solved.
Try just topping off first but if it comes back or you get a check engine light with a p0128 code, you might just want to replace the thernostat. It takes about 30 minutes labor and top up the coolant again (you lose some coolant removing the old thermostat). Mike at Eurotoys should be able to do it no sweat.
More info here: https://www.jaguarforums.com/forum/x...ing-cel-61749/
Hope this helps
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#8
Location of Temp Sensor
I had the fault code from my temp sensor. I understand that contacts can get dirty, do need to clean them. It only showed up once.
Can someone help with the location of the sensor. If it is not too bad to get at, I' ll have a go at it. XKR 2008 Coupe
Tx.
Howell Owens
Can someone help with the location of the sensor. If it is not too bad to get at, I' ll have a go at it. XKR 2008 Coupe
Tx.
Howell Owens
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sam1977
XJ XJ6 / XJR6 ( X300 )
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11-16-2019 11:16 AM
bad, engine, fault, indication, indicator, jaguar, motor, normal, ohm, resistance, sensor, temp, temparature, temperature, warning
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