Powertrain, generic · Fuel and air metering

P0119 Engine Coolant Temperature Sensor 1 Circuit Intermittent/Erratic

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

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.

Likely causes

Loose contact or corroded connector pins
Harness chafing that briefly grounds or opens with engine movement
Sensor with internal crack or contact fault
Air pockets at the sensor (poorly bled cooling system)

Symptoms

  • Check engine light on
  • Temperature gauge jumps
  • Radiator fan switches on for no reason
  • Occasional rough running or idle fluctuation

Repair estimate

DifficultyMediumDIY possible
Parts and labour€20–200
Time0.5–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

engine coolant temperature sensorengine coolant temperature sensor wiring

Related codes

P0117P0118P0116P0115P2186

References: law.cornell.edu, gsi.ext.gm.com, saabwisonline.com, fordservicecontent.com.