P0118

What does P0118 mean?

The coolant-temperature signal reads high (open circuit or very cold).

Can I drive with P0118?

A steady check-engine light with the car otherwise behaving normally usually means you can drive carefully to get it diagnosed — but a flashing light, shaking, lost power, or a strong fuel smell changes that. When in doubt, treat it as more serious. See Can I Drive It? for a quick read on your exact symptoms.

Common symptoms

• Check engine light
• Cooling fan running oddly
• Hard starts
• Poor fuel economy
• Temperature gauge reading oddly

Possible causes

Possible causes include — not “the part is definitely bad”:

• An open circuit or connector fault
• A failing sensor
• Low coolant

What P0118 does not prove

It does not prove the coolant sensor or thermostat has failed on its own — wiring, connectors, and actual cooling-system condition all have to be considered.

What you can safely check

• Whether the temperature gauge and warning behave normally
• The coolant level once the engine is cold — never open a hot system
• Whether the light is steady or flashing

What a shop may check

An example diagnostic direction, not a guaranteed procedure:

• Scan tool and live coolant-temperature data
• The sensor wiring and connector
• A comparison against actual engine temperature
• The thermostat if temperature control is off

What not to do

• Don’t open a hot cooling system
• Don’t assume the thermostat or sensor without confirming

Generic OBD-II guidance — manufacturer-specific codes and causes vary by make, so always confirm against your vehicle. A code identifies a system or condition; it does not, on its own, prove which part has failed.