When to Replace a Coolant Temperature Sensor
If your car has starting problems and the “check engine” light doesn’t come on, you may have a bad engine coolant temperature sensor (ECT). The good news? They’re quick and easy to replace.
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See the crack in the engine coolant temperature sensor pictured? This sensor didn’t set off a trouble code or “check engine” light. But the owner had to pump the gas pedal in the morning to keep the engine running.
The computer in every fuel-injected car must know two things before it can figure out the correct cold-start air/fuel mixture: the engine coolant temperature and the outside air temperature. The situation above points to a bad engine coolant temperature sensor (ECT). The computer is calculating an air/fuel mixture that is too lean. That’s why pumping the gas pedal keeps the engine running.
You can have a bad sensor even without a “check engine” light or trouble code. We could tell you how to test it, but they’re so cheap (about $15) and easy to replace, that it makes more sense to just replace it. Ask the auto parts store clerk to find the right sensor for you (you may have two-one for the computer and one for the temp gauge on your dash) and to show you where it installs on your engine.