Fault codeP0125

Insufficient Coolant Temperature for Closed Loop Fuel Control

What this code means

Insufficient Coolant Temperature for Closed Loop Fuel Control.

P0125 is a generic code: it means the same thing on every make. P0125 belongs to family P01xx — Fuel and air metering. Its page explains how to read a code and groups all its codes by part.

Coolant temperature sensor

This sensor, screwed into the cooling circuit near the cylinder head, tells the control unit how warm the engine is. It is one of the most important inputs: it sets the cold-start enrichment, the idle speed, the cooling fan and the moment the mixture regulation switches to closed loop.

What you notice

Hard starting, black smoke or high consumption when the control unit believes the engine is cold; a cooling fan running all the time, or a temperature gauge that does not match reality.

How to check it

Engine cold, Klaro's coolant temperature should be close to the outside temperature; it should then rise steadily as the engine warms. A reading that jumps or stays at −40 °C points to the wiring or connector. Also check the coolant level: a sensor sitting in air instead of liquid reads wrong.

Watch it live in Klaro

With an OBD2 adapter plugged in, these live readings show the part at work, when your car reports them:

• Coolant temperature
• Intake air temperature
• Time since engine start

What to do

Have it checked this week. The car remains usable, but the fault will not clear itself and will fail the roadworthiness test.

How to read this code

• PPowertrain
• 0standardised code
• 1Fuel and air metering
• 25P0125

Other codes for the same part

• P0115Engine Coolant Temperature Circuit Malfunction
• P0116Engine Coolant Temperature Circuit Range/Performance Problem
• P0117Engine Coolant Temperature Circuit Low Input
• P0118Engine Coolant Temperature Circuit High Input
• P0119Engine Coolant Temperature Circuit Intermittent
• P0126Insufficient Coolant Temperature for Stable Operation