Peugeot P0118

Coolant temperature sensor high input on Peugeot — very often the sensor itself on PSA engines, with corroded plugs close behind.

Peugeot P0118 — Coolant temperature sensor high input on Peugeot — very often the sensor itself on PSA engines, with corroded plugs close behind. Typical UK independent garage cost: £35–£220.

What actually causes P0118 on a Peugeot

On the 1.6 HDi and BlueHDi the coolant sensor lives in the thermostat housing at the end of the head, right beside the gearbox. It gets heat-soaked constantly, and the sensors fail open-circuit more than on most makes. On the 1.2 PureTech it sits in the plastic water outlet, and coolant weeps from that outlet onto the plug. PSA cars also tend to show the fault as a flashing temperature warning or "engine fault: repair needed" on the dash, with the fans running continuously. On some 208 and 2008 models the ECU drops into a reduced-power mode to protect the engine because it can't trust the temperature reading. Owners often think it's a big job, but on most Peugeots this is a sensor and a coolant top-up.

Peugeot engines that log P0118

• 1.6 HDi / BlueHDi DV6 (208, 308, 2008, 3008, Partner)
• 1.2 PureTech EB2 (208, 308, 2008)
• 1.6 THP / VTi Prince (208, 308, RCZ)
• 2.0 HDi / BlueHDi DW10 (508, 3008, Expert)

How we diagnose P0118 on a Peugeot

1. Check live data for an impossible coolant reading (very cold on a warm engine, or jumping around)
2. Feel the top hose and check the coolant level and expansion tank to rule out genuine overheating
3. Inspect the sensor plug at the thermostat housing or water outlet for corrosion and coolant contamination
4. Resistance test the sensor. Open circuit or wildly out of range means a new sensor
5. Fit the sensor with a new clip or O-ring, top up with the correct PSA coolant, bleed through the housing bleed screw, clear codes and road-test

The common misdiagnosis to avoid

Condemning the water pump or head gasket because of the temperature warning. On PSA cars the "engine temperature too high" message can be triggered by a false sensor reading. If the top hose is only warm and the coolant isn't boiling or being pushed out, it's almost certainly the sensor or its plug, not a head gasket.

Peugeot P0118 repair cost in the UK

Expect £35–£220 including parts and labour at an independent garage. Main-dealer quotes on Peugeot are usually higher for the same job, and the spread exists because the cheap cause and the expensive cause throw the same code — pay for the diagnosis before you pay for parts.

Bob's workshop tip

On a 1.6 HDi, take the air intake pipe off first and the sensor comes out in five minutes. Don't let anyone quote you hours of labour for it.

Codes usually seen alongside P0118 on Peugeot

• P0117
• P0116
• P0128
• P0480

Symptoms drivers report with P0118

• The cooling fans running at full blast even when you've just started the car from cold.
• The car is a nightmare to start in the morning, chugging like an old tractor.
• The temp gauge on the dash is completely dead or jumping erratically.
• Black smoke out the back and a strong smell of unburnt petrol/diesel.
• The stop-start system has completely stopped working for no apparent reason.

Repairs that clear P0118

• Replace ECT sensor
• Repair wiring

For the generic, all-makes explanation of this code — meaning, every known cause and UK cost bands — see our P0118 guide.

Reading P0118 on a Peugeot properly

A generic reader will show P0118 and nothing else. What matters is the freeze-frame data stored with it — engine speed, load, coolant temperature and fuel trims at the moment the fault was logged — plus whether any other module on the Peugeot has logged something at the same time. Codes rarely arrive alone, and the order they were stored in usually points at which one is the cause and which are the consequences.

Clearing P0118 without fixing it

Erasing the code resets the Peugeot's readiness monitors as well as the light. The fault returns on the next drive cycle if the cause is still there, and in the meantime the incomplete monitors can stop the car passing an emissions check. After a genuine repair, the car is driven until the relevant monitor completes before it is handed back.

Bob's Mechanical Repairs is an independent garage in Birnam, Dunkeld, Perthshire, with 32 years of Bob's experience on the tools. If P0118 is showing on your Peugeot, bring any scan results with you — we will read the live data ourselves, confirm which cause it actually is, and price the repair before any work starts.