ECT circuit reading above maximum voltage — often an open circuit.
P0118 — also written PO118, P 0118, 0118 — is the OBD-II code for engine coolant temp sensor high input. Same code, same fix: this page covers every spelling of it.
This code usually means your ECU has lost contact with the temperature sensor, making it think the engine is freezing even if it's boiling hot. It's a classic plague on VAG 1.9 PD engines and older Vauxhalls.
P0118 is a sensors fault code, typically costing £35–£220 to put right in a UK garage.
What P0118 actually feels like to drive
- 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.
What causes P0118?
- Failed ECT sensor
- Broken wire
- Corroded connector
UK vehicles that throw P0118 most often
- Vauxhall Corsa D 1.2/1.4 (A12XER/A14XER) 2006-2014
- Volkswagen Golf MK5/MK6 1.9 & 2.0 TDI (BKD/BLS) 2004-2012
- Peugeot 207 1.4/1.6 VTi (Prince Engine) 2007-2013
- Ford Focus MK2 1.6 TDCi (DV6) 2005-2011
- Audi A3/A4 2.0 TDI (CAGA/CAHA) 2008-2015
- Skoda Octavia 1.6 TDI (CAYC) 2009-2013
How P0118 is fixed
- Replace ECT sensor
- Repair wiring
The P0118 misdiagnosis that wastes money
I've lost count of how many thermostats and water pumps I've seen replaced in error for this one. Because the ECU thinks the engine is bone-cold (it defaults to -40°C when the circuit goes open), it dumps way too much fuel in. Owners see the temp gauge sat on zero and assume the thermostat is stuck open. In reality, it's almost always a green, crusty connector or a snapped wire on the loom side, especially on those older French cars where the loom rubs against the gearbox housing.
What a UK garage should charge for P0118
For a basic job on a Corsa or Golf, you’re looking at £40 to £60 for a decent Bosch or Febi Bilstein sensor from a factor like Euro Car Parts. Add an hour’s labour at £60–£90 depending on your local Indy rates. Total bill is usually around £110. If you go to a main dealer, expect to pay £150+ just for the 'diagnostic fee' before they even touch a spanner. If the loom is frayed, expect another hour of labour for a proper solder-and-shrink repair.
P0118 repair cost in the UK
Most P0118 repairs land between £35–£220 including parts and labour. The spread is wide because the cheap fix (a sensor, a hose, a leak) and the expensive fix (a major component) throw the same code — which is why a proper diagnosis before parts are bought saves the most money.
Bob's tip on P0118
Before you let a garage charge you for a new sensor, ask them to 'bridge the pins' on the connector with a paperclip. If the live data on their scanner jumps from -40°C to +140°C, the wiring is fine and the sensor is definitely dead. If it stays at -40°C, a new sensor won't fix a damn thing—you've got a wiring break. Don't let them 'parts-cannon' your car; insist on a basic circuit continuity test. It takes five minutes but saves you £100 in unneeded parts.
Can you drive with P0118?
Yes but fans may run constantly.
Urgency: medium.