P0119Engine Coolant Temperature Sensor 1 Circuit Intermittent/Erratic
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- The engine coolant temperature sensor 1 is an NTC thermistor: the control module feeds 5 V through a resistor, and as the coolant warms the resistance and signal voltage fall. Its value drives cold-start enrichment, idle speed, ignition timing, the radiator fan and the release of closed-loop mixture control. Some Ford engines measure cylinder head temperature instead and calculate a coolant value from it. Coolant temperature can only change slowly because of the thermal mass involved. P0119 is set when the reading jumps faster than physically possible. GM calculates, every second, a window for the next valid value from the previous reading and a sensor time constant of 13 s; readings outside it in three of four samples count as a fault, monitored continuously over two trips. GM/Saab set it after more than 4 s of abrupt changes and then run the radiator fan. Typical causes are loose contacts or a harness chafing as the engine moves.
- What you may notice
- Check engine light on
- Temperature gauge jumps
- Radiator fan switches on for no reason
- Occasional rough running or idle fluctuation
- Likely causes
- LikelyLoose contact or corroded connector pins
- PossibleHarness chafing that briefly grounds or opens with engine movement
- PossibleSensor with internal crack or contact fault
- RareAir pockets at the sensor (poorly bled cooling system)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €20 – €200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.