If I unplug the ECT switch will the engine still run hot

Tiny
STEPHIESMAN
  • MEMBER
  • 1995 TOYOTA CAMRY
  • 2.2L
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 273,350 MILES
Yesterday it started running hot because the fans were not coming on, I unplugged the ECT sensor and they came on, but it would still ran hot.

I know it is a dumb question, but I am still trying to learn, and I really do not have the money to replace it. :/

If I unplug it and the fans run, but it still runs hot, is it because it is unplugged, or because something else is wrong?
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Thursday, February 23rd, 2017 AT 9:50 AM

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Tiny
STEPHIESMAN
  • MEMBER
Update: I have replaced the ECT switch and sensor and the problem still persists, but now there is a CEL. The OBD1 gave me code 22, but I have no idea why it would still be doing the same thing. Please help.
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Thursday, February 23rd, 2017 AT 12:51 PM
Tiny
CARADIODOC
  • EXPERT
Code 22 Water temperature sensor circuit fault

First of all, what are the exact symptoms that tell you the engine is running too hot? The fault code is the result of unplugging the two-wire coolant temperature sensor while the ignition switch was on. The Engine Computer turns on the radiator fan relay when a specific coolant temperature is reached. Logic would dictate it would not do that with the sensor unplugged, but in fact, most computers have a back-up strategy whereby it turns the relay on when there is a fault detected in the sensor circuit. The computer knows it cannot rely on the sensor to provide accurate information, so it turns the fan on just in case the engine is going to run hot. That is why the fan runs when you unplug the sensor. That is a quick way to determine if the rest of the radiator fan circuit is working. You will want to erase the fault code when you are done so it does not confuse the next person who reads the codes.

Most engines of this era use a second coolant temperature sensor for the dash gauge. That one has just one wire.

A defective or unplugged coolant temperature sensor will not cause an engine to run hot, at least not directly. It simply reports what it sees. In some cases it can cause overheating indirectly, not from an engine defect, but from the computer not turning the fan on when it should.
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Thursday, February 23rd, 2017 AT 4:18 PM

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