I have two 2003 Discovery II's and this my first post on the forum. Both Disco's have the genuine 180 thermostat (warm weather thermostat) My one Disco runs great, temp hovers between 186 and 188 on the highway and 195-97 in stop and go traffic. My other Disco which we installed a new water pump and radiator several months ago now has been throwing P0126 codes. I have switched out different thermostats and the code keeps occurring. I did try a regular thermostat a dn ran OK for a couple of days at 205 and got the code again.....maybe a fluke, I am not sure. My mechanic and I can't figure it out. Has anyone run into this issue before? Also, mechanic feels very strongly we should be running temp between 205 and 215, but I totally worry about running these Disco's at these higher temperatures. Appreciate any advice or ideas. Thanks

 

I'm not totally up on your situation and I'm even a little fuzzy on my own details because it was a few years ago, but I'll throw out what I know. I bought an 03 which the PO told me was having a problem with a temp-related code and I'm pretty sure it was related to the radiator not having a sensor below the lower hose connection. The engine was toast and when I swapped in the 04 engine and radiator I found a dangling plug in the engine bay that I connected to my 04 radiator, which did have the sensor in it. Have never gotten any codes with this truck. Hope it helps...

 

SAI D2's & a 180F thermostat = you will get P0126 faults as the two sensors see the engine isn't up to temp in a certain time frame. Nothing to worry about honestly.

 

Thanks. I am using an ultra gauge which shows me the code and soon after the code hits, the engine light kicks on. Anyway to disable it?

 

Maine17..your not alone. I am experiencing the same thing with my 2004. I do realize it's nothing to worry about but when you have an Ultragauge barking at you every time you drive the truck it is an annoyance to have to hit the reset each time..
I too would love to hear how to make the alerts go away and keep the service engine light from reoccurring.

 

Well, I changed my thermostat and put in a good old OEM one in. After two days of driving, the engine light came on again as well as the P0126 code. Does anyone have any ideas on how to resolve this issue?

 

Is it possible that the temperature sensor is faulty? Not sure how to test that, but a replacement might be in order.

 

Beat me to it. The easiest would be to swap with a known good sensor however there's likely an ohm spec somewhere. Also, my 03 has a different style connector than my 04 does for coolant temp so be mindful of which one your harness uses.

 

Thanks! I will try that and see what happens.

 

Hi all - I believe I saw a response about this but my ‘01 is doing the same thing P0126. I’ve got a 180 in it and I just keep clearing the code with my Scan Gauge. I assume this is ok? Mine has 240k miles on it but I live in the desert. Medium temps around town it stays 182-195.