P0115

Engine Coolant Temperature Sensor 1 Circuit

Car Fault Codes Cooling & lubrication

Can you still drive? With care, short trips only

Who can fix it? DIY with some experience

Typical repair time 20 minutes – 2 hours

Typical cost SAR 80 to 500

What it means

The engine computer has detected an invalid signal from the engine coolant temperature (ECT) sensor. This sensor is one of the computer's key inputs for fueling, ignition timing and fan control, so the computer may run the fans constantly and use a backup value for protection.

Symptoms5

Check engine light on.
Radiator fans running constantly, even with a cold engine.
Hard starting or rough idle.
Illogical temperature gauge on some cars.
Higher fuel consumption or black smoke.

Possible causes5

Unplugged connector or one corroded by leaking coolant.
Open or shorted sensor wiring.
Failed coolant temperature sensor.
Weak ground shared with other sensors.
Engine computer fault (rare).

How to diagnose5

First check the coolant level and make sure the engine is not genuinely overheating.
Watch the coolant temperature reading on a scan tool; a reading stuck at the lowest or highest possible value means an electrical fault.
After a long rest, compare the reading with intake air and outside temperature.
Inspect the connector and wiring for corrosion or coolant residue.
Measure the sensor resistance and compare it with the manufacturer table.

How to fix4

Clean and reconnect the connector, and fix any coolant leak dripping on it.
Repair the open or shorted wire.
Replace the coolant temperature sensor, then top up and bleed air from the cooling system.
Clear the codes and confirm the reading rises steadily as the engine warms and the fans switch on at the right time.

Repair cost

0–500

500–2,000

2,000–5,000

5,000+

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is low for a connector or wire repair, and a little higher when the sensor is replaced and coolant added, especially if it is hard to reach.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions

Why do the fans run all the time with this code?

Because the computer cannot trust the engine temperature reading, so it runs the fans as a precaution to protect the engine from overheating.

Can I drive with this code?

Short distances and carefully, while watching the temperature gauge and coolant, because the computer may not detect real overheating in time.

This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.

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