Coolant Temperature Sensor Replacement

Updated: Feb. 28, 2023

Visually inspect the engine coolant sensor because it may not set off a trouble code.

engine-coolant-temperature-sensorFamily Handyman
If you have starting problems and the 'check engine' light doesn't come on, you may have a bad engine coolant temperature sensor (ECT). They're quick and easy to replace.

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Solution to a starting problem

Bad coolant temperature sensor causes cold starting problems

See the crack? This sensor didn’t set off a trouble code or “check engine” light. But the owner had to pump the pedal to keep the engine running.

If you have to pump the gas pedal in the morning to keep your car running, you may have a bad engine coolant temperature sensor. 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. Your symptoms are a dead ringer for 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 your 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 an engine coolant temperature sensor. 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. This is one of those repairs you don’t need to bring your car to the shop to get fixed.

Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • Wrench set

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.

  • New engine coolant temperature sensor