I have a family member who has a 2006 Jaguar X-TYPE with the Ford 2.5 V6 engine. They had a problem about a year ago where the coolant temperature gauge would suddenly shoot up from halfway to red and a red warning light would come on, indicating that it was overheating. They took it to a garage, which diagnosed a faulty coolant temperature sensor, which was replaced. The car was fine for a few weeks, then the same thing happened again and has recurred about once every couple of months since.
When the light comes on, they pull over and check under the bonnet, but there is no overheating or bubbling in the coolant bottle and there are no driveability issues. One of the times the red overheating light was on after the car was parked overnight, suggesting the car was giving a false reading. A code reader found the code ‘P0116’, indicating the CTS. I deleted the code and ran the car up to temperature and the code didn’t return. On live data, the coolant temperature goes up to around 96°C until the fans kick in.
Reading through various forums on the internet, people suggest it’s a faulty thermostat, which seems to be a common problem. Other people say that there are two coolant temperature sensors on the
2.5, but no one seems to know where they’re located. Would you agree that replacing the thermostat and other CTS is the next step? Or do you know of any other common problem? Also, do you have any info of where the second CTS is located? Daniel Clark Neither Autodata nor the Jaguar Technical Information System have any information on a second coolant temperature sensor, and I believe that some people may be getting confused because some 2.5 V6 engines had a cylinder block heater unit.
As the light was illuminated at startup on one occasion, and as the cooling fan appears to operate correctly with no signs of boiling or overheating, I doubt that the thermostat is the source of the problem. I would look for a possible electrical fault in the system. The full description of the ‘P0116’ code is ‘Engine coolant temperature (ECT) sensor – range/performance problem’. This code appears if the engine control unit detects either a slow or rapid change in the coolant temperature which does not match the readings given by the air intake temperature sensor (IAT). The variation in reading which is sufficient to trigger the code is built into the ECU as an algorithm and it is possible that, when a warm engine is restarted, the conditions can allow the code to be triggered.
The most likely causes of the problem are either a poor connection at the CTS terminals or a breach within the wiring loom. As the coolant gauge appears to read correctly most of the time, and the cooling fans kick in at the correct temperature, I would also check the air intake sensor reading to ensure that this isn't confusing the ECU. There is also a very slim chance that the ECU itself is at fault, but this would be very rare.
In conclusion, because the problem appeared to be rectified for a short while after the CTS was replaced, this could have been because the wiring loom was moved. This movement of the loom could have possibly altered the position of the wires, inadvertently fixing the problem for a short time. Methodical checking of the wiring between the sensor and the ECU would be my recommendation.
The reader's Jaguar X-TYPE indicates that it is overheating, but is actually running normally.