ECT Malfunction?

soonersubie · 11-27-2001, 01:09 PM

I have an OBD-2 scanner, and recently pulled a code on a MY95 Impreza 2.2L. The code was P0115 Engine Coolant Temperature Circuit Malfunction. I cleared the code, and the CEL light stayed off for 2 days, and has now come back on.

My question is: Why is this occuring if the coolant temp. guage is operating normally, there are no coolant leaks, and the coolant level is to the full mark? I did a visual inspection on the wires leading to the ECT sensor, and saw no obvious signs of corrosion, broken wiring, etc. Could this just be an internal malfunction of the ECT sensor? Any help would be greatly appreciated. Thanks in advance.

James

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Puckaveli · 11-27-2001, 03:03 PM

Is your obd-2 giving you an ECT reading? I know the fans kick in at 190 and the temp never really gets any higher than that. If your getting a crazy ECT reading then I would assume it would be the sensor that reads the temp. I unfortanatly don't know where it is.

mrbell · 11-27-2001, 04:26 PM

sounds like you've got a broken sensor to me...

soonersubie · 11-27-2001, 05:13 PM

mrbell, how is it that the temperature sensor is broken if the coolant temperature guage in the instrument panel seems to be working fine? Thanks.

James

SubyTechMaster · 11-27-2001, 10:24 PM

Coolant Temp. Ga. sending unit is a simple thermister to ground, seperate from the ECT. This is a gauge sending unit and not intended to be real accurate.

ECT is a self-contained Thermister with a 5V referance signal supplied by the ECU and the ECU reads the residual voltage. The ECT is a very accurate sensor. It's possible you have resistance in the circuit or more likely, you have a bad ECT sensor. The ECU picks this up as a reading inconsistant with it's data base. If you have an open in the circuit your Radiator Fans will come on full speed with the CEL. If your fans are not coming on, your sensor is probably showing open briefly when it is cold, which is fairly common. What does the Freeze Frame say?

soonersubie · 11-28-2001, 12:49 AM

So, SubyTechMaster, you are saying that the coolant temperature sending unit is completely different from the ECT sensor, right? If this is the case, can you tell me where the ECT is located, because I may have been checking the wiring to the coolant temperature sending unit instead of the ECT sensor.

Concering the fans, they are off when the light comes on, and seem to be functioning properly.

If the wiring/connections to the ECT sensor look OK, would I be correct in assuming that there is a malfunction within the ECT sensor itself? Should I just replace the ECT sensor in this case? Thanks.

James

11-27-2001, 01:09 PM	#1
soonersubie Scooby Newbie Member#: 11896 Join Date: Nov 2001 Location: Okla. City, OK, USA Vehicle: 1995 Impreza L AWD White	ECT Malfunction? I have an OBD-2 scanner, and recently pulled a code on a MY95 Impreza 2.2L. The code was P0115 Engine Coolant Temperature Circuit Malfunction. I cleared the code, and the CEL light stayed off for 2 days, and has now come back on. My question is: Why is this occuring if the coolant temp. guage is operating normally, there are no coolant leaks, and the coolant level is to the full mark? I did a visual inspection on the wires leading to the ECT sensor, and saw no obvious signs of corrosion, broken wiring, etc. Could this just be an internal malfunction of the ECT sensor? Any help would be greatly appreciated. Thanks in advance. James * Registered users of the site do not see these ads.

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11-27-2001, 03:03 PM	#2
Puckaveli Scooby Specialist Member#: 1518 Join Date: May 2000 Location: Stow, OH Vehicle: 00 2.5RS Silver	Is your obd-2 giving you an ECT reading? I know the fans kick in at 190 and the temp never really gets any higher than that. If your getting a crazy ECT reading then I would assume it would be the sensor that reads the temp. I unfortanatly don't know where it is.

11-27-2001, 04:26 PM	#3
mrbell Scooby Specialist Member#: 1871 Join Date: Jul 2000 Location: Salt Lake City, UT Vehicle: 2000 Impreza 2.5RS Blue Ridge Pearl	sounds like you've got a broken sensor to me...

11-27-2001, 05:13 PM	#4
soonersubie Scooby Newbie Member#: 11896 Join Date: Nov 2001 Location: Okla. City, OK, USA Vehicle: 1995 Impreza L AWD White	mrbell, how is it that the temperature sensor is broken if the coolant temperature guage in the instrument panel seems to be working fine? Thanks. James

11-27-2001, 10:24 PM	#5
SubyTechMaster Scooby Specialist Member#: 4423 Join Date: Feb 2001 Location: Placerville, CA USA Vehicle: '04 08 Tribeca, SVX Gold, Maroon	Coolant Temp. Ga. sending unit is a simple thermister to ground, seperate from the ECT. This is a gauge sending unit and not intended to be real accurate. ECT is a self-contained Thermister with a 5V referance signal supplied by the ECU and the ECU reads the residual voltage. The ECT is a very accurate sensor. It's possible you have resistance in the circuit or more likely, you have a bad ECT sensor. The ECU picks this up as a reading inconsistant with it's data base. If you have an open in the circuit your Radiator Fans will come on full speed with the CEL. If your fans are not coming on, your sensor is probably showing open briefly when it is cold, which is fairly common. What does the Freeze Frame say?

11-28-2001, 12:49 AM	#6
soonersubie Scooby Newbie Member#: 11896 Join Date: Nov 2001 Location: Okla. City, OK, USA Vehicle: 1995 Impreza L AWD White	So, SubyTechMaster, you are saying that the coolant temperature sending unit is completely different from the ECT sensor, right? If this is the case, can you tell me where the ECT is located, because I may have been checking the wiring to the coolant temperature sending unit instead of the ECT sensor. Concering the fans, they are off when the light comes on, and seem to be functioning properly. If the wiring/connections to the ECT sensor look OK, would I be correct in assuming that there is a malfunction within the ECT sensor itself? Should I just replace the ECT sensor in this case? Thanks. James