P0117 code meaning
Engine Coolant Temperature Sensor 1 Circuit Low
Powertrain system Generic code P01xx codes Check engine light
What P0117 means
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. P0117 means the signal voltage is too low, so the sensor would report an implausibly hot engine (around 140–160 °C). Usual causes are a signal wire shorted to ground, coolant or moisture in the connector, or an internally shorted sensor. Limits: GM below 55 ohms, Ford gasoline below 0.244 V for 5 s, Ford diesel below 0.10 V, Mitsubishi below 0.1 V for 2 s. Mitsubishi then calculates with 80 °C; GM/Saab switch the radiator fan on and the A/C compressor off. GM needs two trips. On Ford engines with a head temperature sensor the equivalent is P1290.
P0117 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 1.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0117
- Check engine light on
- Radiator fan runs constantly
- Hard cold start (no enrichment, engine reported hot)
- Temperature gauge at hot end
- A/C may be switched off
Common causes of P0117
- Most likelySignal wire shorted to ground (chafing, pinched harness)
- Most likelySensor shorted internally or coolant inside the sensor
- PossibleMoisture or coolant in the connector
- Less likelyEngine control module faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Engine coolant temperature sensorEngine coolant temperature sensor wiring
What each part of P0117 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 1 | Area: fuel and air metering. |
| 17 | The exact fault in that area. |
What to do next
- Note P0117 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0117
What does P0117 mean?
P0117 means "Engine Coolant Temperature Sensor 1 Circuit Low". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P0117?
Drive gently and only to a workshop. With P0117 the car can go into limp mode (reduced power) to protect itself.
Will P0117 fail an emissions test?
Yes, it can. P0117 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0117 to fix?
Difficulty: easy. A typical repair takes 0.3 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0117 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.