2000 Ford Escort ZX2, 105k miles, automatic.

The service engine light came on, so I stopped so I could at least check the obvious stuff, including fluids. My coolant was pretty low, so I topped it off.

Service engine light stayed on, so I went to get the reading on it - "P0125 - coolant temp is always low." Probable causes: 1) Coolant level off - fixed that. 2) Defective Thermostat - that was replaced a few months ago. 3) Engine Coolant Temperature sensor defective.

Absolutely no symptoms in operation. No noticeable leaks. My temp gauge on the dashboard reads normally, everything warms up fine, and my heat works great inside. Idle, acceleration, etc. all appears normal. The only possible effect is I might be losing some mpg - unsure until my next fill-up, because the gas gauge isn't the most accurate thing in the world. But my fuel is dropping at a faster rate than normal, according to the gauge.

As I said, we replaced the thermostat a few months ago, and my coolant level is normal. Where do I go from here? If it is the sensor, can I just ignore it, or will that actually cause damage somehow? Could my new thermostat still be the problem, or would some other issue cause the thermostat to fail?

[Edited on November 15, 2008 at 10:11 AM. Reason : a]

11/15/2008 10:03:42 AM

the sensor is located on the drivers side front of head near the thermostat, the one with two wire/pins the single wire one is for the gauge

disconnected, it should read ~200 ohms across the terminals, and ~70 ohms hot

they are cheap anyway, so it in doubt, swap it out

remember, unless you clear the codes with a reader, or disconnect the battery, it will take a while for the code to clear itself if it was related to the water level

the gauge sensor is independant, the ect temp sensor determines fuel/air ratio and will probably cause your car to run rich as hell, eventually fouling the plugs or plugging the cat

http://www.partsamerica.com/ProductDetail.aspx?MfrCode=FAA&MfrPartNumber=36447&PartType=290&PTSet=A

[Edited on November 15, 2008 at 11:17 AM. Reason : link]

11/15/2008 11:13:22 AM

it's the coolant sensor. there are two on most cars.. I'll just assume dookiemaXXX is right on the rest of the details and say do what he said

11/15/2008 11:42:35 AM

Quote :

"the sensor is located on the drivers side front of head near the thermostat, the one with two wire/pins the single wire one is for the gauge disconnected, it should read ~200 ohms across the terminals, and ~70 ohms hot they are cheap anyway, so it in doubt, swap it out remember, unless you clear the codes with a reader, or disconnect the battery, it will take a while for the code to clear itself if it was related to the water level the gauge sensor is independant, the ect temp sensor determines fuel/air ratio and will probably cause your car to run rich as hell, eventually fouling the plugs or plugging the cat http://www.partsamerica.com/ProductDetail.aspx?MfrCode=FAA&MfrPartNumber=36447&PartType=290&PTSet=A [Edited on November 15, 2008 at 11:17 AM. Reason : link]"

Thanks! How long should I wait before changing the sensor to see if the code will clear itself? A few days?

11/15/2008 3:00:44 PM

just pull the battery cable

[Edited on November 15, 2008 at 3:03 PM. Reason : asdf]

11/15/2008 3:02:42 PM

ah, good call, missed that part

11/15/2008 3:31:45 PM

knowingly driving a vehicle around with the check engine light on is extremely irresponsible and environmentally unfriendly. not to mention illegal. then we also have the possibility of it leaking coolant.

clearly, you are a hypocritical asshole. i feel obligated to report your violations to the DMV.

11/15/2008 3:41:38 PM

Be my guest.

11/15/2008 3:52:14 PM