If you enjoy reading about cars and other related topics, we’d love to share our Auto Care Blog with you. At CARS of America, Inc., our highly trained auto mechanics deliver the very best in auto repair services through our two locations in Glenview. One way we accomplish that is in the time we take to help educate our customers so they feel confident making auto repair decisions. Our Auto Care Blog is just one way we meet that goal. Let us know if there’s a topic you’d like to hear more about!


‘Check engine’ light on? Could be the engine coolant temperature sensor

Your car’s “Check Engine” or “Service Engine Soon” light can flash on for more than 1,400 different reasons, and in the coming months, we’re going to share with you what some of those reasons are. The light is part of your vehicle’s on-board diagnostics (OBD) system and can indicate anything from a quick fix like a loose gas cap to a major repair like a catalytic converter.

Trouble code

P0115 – Engine Coolant Temperature (ECT) Circuit Malfunction

The engine coolant temperature sensor measures the ever-changing engine coolant temperature. It provides important data that helps the powertrain control module (PCM) to control the air fuel ratio, ignition spark timing, the cooling fans and many components of the emissions control systems.

The ECT sensor essentially is a thermistor that changes resistance with temperature. As the temperature of the coolant changes, the resistance changes on the ground signal to the powertrain control module. When the engine is cold, the resistance is high. When the engine is warm, the resistance is low. If the PCM detects a voltage condition that seems abnormally low or high, the P0115 error code will set. The check engine light will always light up if this code is set.

If your car is having problems with the circuit, you might notice:

  • The vehicle might be hard to start.
  • It might blow a lot of black smoke and run extremely rich.
  • The engine might want to die or backfire in the tailpipe.
  • Cooling fans might run all the time when they shouldn’t be, or not at all when they should be.

If this error occurs, it typically is because of a bad ECT sensor, but it also could be that the wiring or connector is damaged at the sensor, there is an open or short in the signal circuit, or the powertrain control module is damaged or broken.

Engine light on? Give CARS of America a call at 847-724-6724 or schedule an appointment.

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