P0118 on a Lexus: Causes, Fixes & Repair Cost

🟠 Moderate severity · drivable

Safe to drive, but the engine may run rich and use more fuel until the sensor circuit is repaired.

What P0118 means on a Lexus

On a Lexus, P0118 means the engine coolant temperature (ECT) sensor is sending a high-voltage signal that the computer reads as the engine being very cold. The ECT sensor on Lexus models is durable, so an open wire or loose connector is more often the cause than a failed sensor. The computer then adds extra fuel as if the engine were always cold.

Is P0118 common on Lexuss?

P0118 is uncommon on Lexus models like the ES, RX, and GX because the sensors are reliable. When it does appear, it is usually on higher-mileage cars where wiring or the connector was disturbed during other service.

Commonly reported on: ES, RX, GS, GX.

Symptoms

Check engine light on
Poor fuel economy
Hard cold start
Engine runs rich

Common causes

most common: Open sensor signal wire
common: Faulty coolant temperature sensor
common: Corroded or loose connector
less common: Wiring disturbed during previous repairs

How to fix it

Fix	DIY?	Typical cost
Replace the coolant temperature sensor	Yes	$30–80
Repair the sensor wiring or connector	Mechanic	$60–150
Have a shop diagnose the circuit	Mechanic	$80–120