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Old 11-17-2007, 07:09 PM   #1
Scooby Newbie
Member#: 159677
Join Date: Sep 2007
Location: Princeton, NJ
1996 Legacy Outback

Default Coolant circuit problem

I replaced the coolant temp. sender (the one that goes to the gauge) this past June because the gauge wasn't moving. That solved the problem and now the gauge is reading accurately.

However, about 2-3 months ago, the CEL came on and when I scanned it I got Trouble Code P0115, which is "Coolant temp. sensor circuit malfunction." I reset it and all was well for a few days until the light came back on. Scanned it, same code; reset it, came back on within a week. I keep getting the same TC, I keep resetting it, it keeps coming back on 2-3 days later.

The sensor, as I mentioned, is new; the gauge is reading fine; and the coolant is within the proper temp. range (measured independent of the gauge).

Any advice?
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Old 11-17-2007, 07:48 PM   #2
Patrick Olsen
NASIOC Supporter
Member#: 120
Join Date: Jul 1999
Chapter/Region: AKIC
Location: Where the Navy sends me...
1997 Legacy 2.5GT
QuickSilver Metallic


There are 2 coolant temperature sending units - a single wire one that drives the gauge in the instrument cluster, and a dual (I think) wire one that feeds the ECU. If I'm reading your post correctly, it sounds like you replaced the one for the gauge, which just has a single wire with a spade connector hooked to it. Am I right?

I doubt the CEL would be tripped by the sending unit that drives the gauge in the instrument cluster. It's more likely it's being tripped by the larger sending unit that feeds the ECU.

Pat Olsen
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