I have a 1996 Legacy Outback that I have a weird problem with. No dealer in the Denver are can give me any ideas, so I thought I'd try here. Irecently had a "check engine" light come on. The culprit ended up being a knock sensor and has since been replaced. The issue is the temperature gauge. At the same time the "check engine" light was coming on, the temp gauge would move straight to normal operating temp as soon as the car was started, even if it was cold. It would even move as soon as power was turned on (key to accesories, etc.) Since the knock sensor was replaced, the "check engine" light has stayed off, and my mechanic told me that no other codes came up, but the tamp gauge activity has continued. I'm thinking bad sensor or gauge itself, but I would think that a code would come up somewhere, wouldn't it? Anyway, just checking to see if anyone has had a similar problem.

There is a code for the coolant temp sensor but I dont think that sensor runs your guage. I belive there are 2 sperate sensors, one for the ECU which would throw a code, and another sending unit just for the gauge. Could be the guage or the sending unit.

 

If you are handy with a multimeter you could do an OHMs resistance test on the guage sending unit. Dealership should be able to provide values for you to refer against. Or just have a mechanic test the sending unit and guage for you

 

Hope this helps!

Yes sir, two separate sensors. Right next to eachother, on the engine block where the coolant pipe leaves and heads for the radiator.

jwjsabin, I dont know what engine you have, but on my 96 2.2L engine, there is only one coolant temp sensor. It sends its info to the ECU which in turn activates the temp gauge. On my 92 Loyale there was indeed two sensors, one with a two wires connector for the ECU and one with only one wire for the gauge. Did Subaru revert to two sensors with the 2.5 L engine?