I have researched this topic and seen a couple conflicting answers. I have a 99 XJ with 4.0L that had the gauge cluster swapped by the previous owner from the base model with dummy lights to the one with oil pressure and temp gauge. I do not know which year model the new cluster came out of. Most of what I have read says the cluster swap is a direct replacement and no need to change the temp sensor. Can someone confirm that? I am currently having an issue with the temp gauge reading real low but above bottomed out but lower than you would expect even if the thermostat is stuck open. I am having some other coolant issues (radiator has a leak and is being replaced). I will have the thermostat checked when radiator is put in and guess I will see if the temp gauge acts differently. Just curious if the cluster swap could be associated with the gauge issue.

 

Never done the swap but I can say with 100% certainty that there's only one coolant temperature sensor on a 99 XJ system and that the ECU provides the info to the gauge cluster. The gauge itself could be having issues. A scan tool will be able to get the temp info from the ECU, allowing you to determine which is the problem....

 

It's possible to read the EEPROM on the speedo and determine what year XJ it came from. But regardless of that, a temp sensor problem would not be related to the cluster. All sensor data goes to the ECU and is then communicated to the cluster via the CCD bus. Temp, fuel level, speed, rpm, etc are all shared via CCD. The only exception is some of the lights are wired up directly such as the 4wd light.

 

The problem with the single sender is that if it reads low, both the scan tool, and the gauge will both read the same..thus single source. It will prove that the gauge is mostly calibrated if it reads similar to scan tool. Only true way to tell is remove sender and drop in pot of boiling water and thensuper quickly or at the same time read resistance with a meter... should be approx 675 to 725 ohm. if much further off than this...its off. lower resistance reads /displays higher temperature.

 

Thanks for the feedback. After going through cooling system with new radiator, water pump, coolant and thermostat, things seem to be in order. Gauge is reading in what I would consider the correct range around 200 +/- when fully warmed up.