What happens when the coolant temp sensor not work?

When the coolant temperature sensor fails, it can lead to inaccurate readings of the engine's temperature, causing the engine control unit (ECU) to mismanage fuel injection and ignition timing. This may result in poor fuel economy, increased emissions, overheating, or even engine damage. Additionally, the vehicle's check engine light may illuminate, and the dashboard temperature gauge may behave erratically. In some cases, it can also cause difficulty in starting the engine or lead to stalling.