EngineLightCodes
Powertrain code

P0119 Engine Coolant Temperature Sensor 1 Circuit Intermittent/Erratic

Severity
Fix soon
Typical repair cost
$20–$220
Do it yourself
Possible, medium
Shop time
0.5–2 hours

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.

How the engine computer detects it

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.

Written from public technical sources and not yet checked by a mechanic. How we write these pages

Symptoms

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

Common causes

  1. Loose contact or corroded connector pins Most likely
  2. Harness chafing that briefly grounds or opens with engine movement Possible
  3. Sensor with internal crack or contact fault Possible
  4. Air pockets at the sensor (poorly bled cooling system) Less likely

How to diagnose P0119

  1. Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
  2. Inspect the parts involved: engine coolant temperature sensor, engine coolant temperature sensor wiring.
  3. Work through the causes above from most to least likely, cheapest checks first.
  4. Clear the code and drive a full drive cycle to confirm the repair held.

Reading the code

P
Powertrain
0
Generic (SAE) code
1
Fuel and air metering
19
Specific fault

Questions drivers ask

Can I drive with code P0119?

Drive gently and only as far as you need to. The engine computer may limit power to protect the engine, so avoid highways and heavy traffic until it's fixed. If the check engine light starts flashing, pull over.

Will my car pass an emissions inspection with P0119?

Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.

Will P0119 clear by itself?

The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.

Can I fix P0119 myself?

Often yes, with an OBD-II scanner and basic tools. Difficulty: medium. Start with the cheapest checks before replacing expensive parts.

This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.