P0119: Engine Coolant Temperature Sensor 1 Circuit Intermittent/Erratic

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.

Symptoms

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

Most 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)

What to check, in order

Start with the simplest. You can tick off each step.

1. With the engine cold, check the coolant level; never do this when the system is hot
2. Gently move the wiring with the engine running and watch whether the reading changes.
3. Check the actual temperature in live data
4. Make sure the fan comes on when it should
5. Check the thermostat and connector
6. Measure the sensor and replace it if its readings do not make sense

Good to know

• Repair difficulty: medium
• It can trigger limp mode.
• It affects emissions.

What each character of P0119 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 1: Air and fuel
• 19: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0119?

Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.

What causes code P0119?

The most common causes are: loose contact or corroded connector pins; harness chafing that briefly grounds or opens with engine movement; sensor with internal crack or contact fault.

Related codes

• P0117Engine Coolant Temperature Sensor 1 Circuit Low
• P0118Engine Coolant Temperature Sensor 1 Circuit High
• P0116Engine Coolant Temperature Sensor 1 Circuit Range/Performance
• P0115Engine Coolant Temperature Sensor 1 Circuit
• P2186Engine Coolant Temperature Sensor 2 Circuit Intermittent/Erratic

Sources

• law.cornell.edu: 13 CCR 1968.2
• gsi.ext.gm.com: 18OBDG04 Engine Diagnostics
• saabwisonline.com: dtc p0117 p0118 or p0119
• fordservicecontent.com: OBD Operations Summary Gasoline 2020 2023

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.