P0119
PowertrainEngine Coolant Temperature Sensor Circuit Intermittent
This is usually a small, cheap job, so don't panic. P0119 means the coolant temperature sensor signal is jumping about instead of changing smoothly as the engine warms, and the ECU has flagged it as intermittent. Because the reading bounces around, the engine management can't trust it, so it leans on guesswork for fuelling and you get the warning light. Most of the time it's a tired sensor or a dodgy connector, both of which are easy fixes.
ⓘ Information only. This page provides general educational information about fault code P0119. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0119 mean?
P0119 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Engine Coolant Temperature Sensor Circuit Intermittent.
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Temperature gauge that flickers or swings from cold to hot for no reason while you're driving
- • Engine warning light on, sometimes coming and going rather than staying solid
- • Worse fuel economy, often noticed as more frequent fill-ups around town
- • Lumpy idle or a brief hesitation when you accelerate from cold
- • Hard starting when the engine is already warm
- • Occasionally the coolant warning light joining in
Possible causes
Causes commonly associated with P0119, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. The coolant temperature sensor itself going intermittent. These are cheap brass-and-plastic parts that crack internally with age, and it's the most common cause by a mile
- 2. Corroded or loose pins in the sensor connector, very common where the plug sits near the engine and gets heat-cycled and damp
- 3. Chafed or broken wiring between the sensor and ECU, often where the loom rubs against a bracket or the manifold
- 4. Air pockets in the cooling system after a coolant change or bleed, leaving the sensor tip sitting in air rather than fluid
- 5. Low coolant level so the sensor isn't properly submerged at certain temperatures
- 6. Sticking thermostat causing the coolant temp to behave oddly, which can mimic a flaky signal
- 7. An ECU input circuit fault, rare and the last thing to suspect after everything else checks out
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Wiggle-test the sensor connector and the loom near it while watching live coolant temp on a scanner. If the reading jumps when you move the wiring, you've found it
- 2. Unplug the connector and look for green corrosion, bent pins, or moisture. A spray of contact cleaner and reseating the plug fixes a fair few of these
- 3. Check the coolant level cold, and top up and bleed if it's low. A system full of air will throw odd readings all day
- 4. Measure the sensor resistance with a multimeter as the engine warms. Most read a few thousand ohms cold dropping to a couple of hundred hot. A reading that jumps or open-circuits points straight at the sensor
- 5. Inspect the wiring run from sensor to ECU for chafe points and breaks, paying attention to anywhere the loom is cable-tied to something that gets hot
- 6. If the sensor, connector and wiring all test fine, look at the ECU input circuit, but that's a long way down the list
Common questions about P0119
How long should this take to sort out? +
If it's just the sensor, a garage will usually have it done inside an hour, often less on engines where the sensor is up top and easy to reach. Most coolant temp sensors are simple to access, though some need a bit of coolant drained first. The job that eats time is tracking down an intermittent wiring fault, which can stretch to two or three hours of diagnostic time because the fault has to be present for them to catch it.
Is a cheap aftermarket sensor fine or should I pay for genuine? +
A decent branded aftermarket sensor from the likes of Bosch, Febi or Hella is perfectly good and usually costs £10 to £30. No need to pay main-dealer money for the genuine part here. What I'd avoid is the unbranded eBay specials at a couple of quid, because a cheap sensor that goes intermittent again puts you right back where you started. Buy a name you recognise and fit it once.
Can I keep driving with this showing? +
For short trips, yes, but I wouldn't leave it. With a flaky temperature signal the ECU can over-fuel the engine, which washes oil off the bores and wastes fuel, and on some cars it'll trigger limp mode or refuse to switch off the cooling fans. Get it looked at soon rather than ignoring it, because the fix is cheap and the running costs of leaving it add up quickly.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →