So i bought this truck a few months ago, slowly fixing little things here and there. Coolant temp gauge always seemed a little off. It always seems to read low on the gauge, even though with the scan tool I read 178 degrees when warmed up. Not knowing history of the vehicle before i bought it, I decided it would be best to replace the water pump and thermostat. bled the system several times, but the gauge almost makes it to the halfway mark where it should be. Now that outside temps are dropping(its about 40 degrees f out now), it the temp gauge stops around 1/4-1/3 hot, not even coming close to the half way mark. Heat blows hot, upper radiator hose is hot, ac fans are not constantly running. replaced viscus fan clutch earlier as well. Figured it war just a temp sensor issue, so i swapped for a new sensor and the gauge doesnt even move. Using the scan tool, i can read temp fine at the ecm, but nothing at the gauge. swapped back to the old sensor, and that didnt change anything either. so following the wiring diagrams, looks like pins 1 and 2 are for the gauge. resistance check from bcm connector g, pin 19 to pin 2 at sensor shows .5 ohms. pin 1 to ground shows resistance of 2.5 ohms. Now I have no gauge reading and stuck for ideas on this one. thanks- jake

 

Should probably mention it’s a 2001 range p38

 

I think the P38'S and D2's all have the same dumb temp gauges that read steady at mid range through a fairly wide coolant temperature range. It seems the original engineers thought this was a good idea. Land Rover isn't the only company that did this. You probably don't have a problem. Many people on this forum recommend getting a Ultra Gauge to monitor the actual temps. I haven't done this myself yet, but plan to soon.

 

Right, most manufacturers use a coolant temp gauge that shows center when warm, but it could be a wide range of temps, as long as its in an acceptable range. My 99 d2 always read dead center after warmed up, but this p38 never even reaches center. ill probably add additional gauge later on, but for now i need to fix this

 

Nice choice of vehicles! I think you'll really love the P38 once it's sorted.

 

May want to consider a replacement temp sender as well just to rule that out.

 

Already did, then the gauge stopped working. Went back to the old sensor and still not working. Checked wiring between sender and becm, all ok, checked ground e1355(I think that’s the number, don’t have the diagram in front of me at the moment). Didn’t check the wiring between instrument cluster and becm, but I didn’t move any of that wiring when installing the sensor, so I’m doubting it’s the issue

 

So I looked in rave, can’t find what I need to diagnose this one. Everything from the coolant temp sensor to the becm operates fine. So now is down to becm, coolant gauge, and wiring between. Is it common for the gauge to stop working on these trucks? That’s kinda what it seems like is the issue but I want to be 100% first. Any good way to test the gauge? I was hoping one of my scan tools would have a gauge sweep test, but no luck