P0117 Engine coolant temperature sensor circuit reads too low (shorted toward ground)

Engine coolant temperature sensor circuit low

Monitor

A low-reading coolant sensor usually causes rich running, fans on and a rough idle rather than damage, but the engine computer then relies on a wrong temperature.

It gets more serious if:

  • Stop: Stop driving and let the engine cool if the temperature gauge or a warning shows the engine is overheating, because P0117 can be set by, or can hide, a real overheating problem.

Source: how we rate severity

P0117 in short

P0117 means the computer sees the coolant temperature sensor signal as unreasonably hot, which usually means a bad sensor or a short to ground in its wiring. Expect rough running, poor mileage and fans running. It is usually drivable, but stop if the engine really overheats.

The coolant sensor changes resistance with temperature, and the computer reads that as a voltage. P0117 sets when the resistance drops so low that the reading would mean a temperature above about 300 F for more than five seconds, which is not realistic.

A failed sensor, a signal wire shorted to ground or a damaged connector are the usual reasons. Because the computer thinks the engine is very hot, it can run rich, turn the cooling fans on all the time and shut off the A/C.

Several carmakers have bulletins naming this code: Chrysler on the 2011 Journey, Ford on 2.7L EcoBoost engines (the fix there replaces the coolant and knock sensors together), and Cadillac on a chafed harness on the 2010 CTS.

Most likely causes

  1. Failed coolant temperature sensor

    Common general cause
    Why it ranks here
    TroubleCodes.net lists a defective coolant sensor first, and a Chevrolet Cruze owner reports a sensor and housing replacement with P0117 and P0118.
    What would change this
    Rises if unplugging the sensor makes the scan tool read about -40 F and the old sensor test out of range. Falls if the sensor reads accurately against real temperature.
    How to test the engine coolant temperature (ect) sensor

  2. Short to ground or damaged wiring in the signal circuit

    Common general cause
    Why it ranks here
    TroubleCodes.net lists a short to ground, damaged harness and loose terminals; Cadillac found chafing where the harness crosses the transmission bellhousing on the 2010 CTS.
    What would change this
    Rises if the code stays after the sensor is unplugged, or the harness shows chafing. Falls if unplugging gives the expected -40 F reading.

  3. Coolant and knock sensor wiring (2.7L EcoBoost, Ford)

    Supported by vehicle data
    Why it ranks here
    Ford SSM 48991 names P0117 among codes that may be due to the coolant temperature sensor or the knock sensor wiring harness, with replacement of both sensors as the repair.
    What would change this
    Rises if you own a listed 2.7L EcoBoost and a dealer confirms coverage. Falls if no bulletin applies.

  4. A genuinely overheated engine

    Possible — needs testing
    Why it ranks here
    TroubleCodes.net lists an overheated engine as a cause, so a real overheating problem can set this code.
    What would change this
    Rises if the gauge or warning shows heat or coolant is low. Falls if the engine runs at normal temperature and the sensor reads wrong.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Compare the scan tool coolant temperature with the real engine temperature on a cold engine and while warming up, and check the coolant level when the engine is cold.

    Low riskTool: scan tool with live data

    • IfThe scan tool temperature is absurdly high on a cold engine, or the engine is truly hot

      It meansCheck for real overheating first.

      Points to: A genuinely overheated engine

    • IfThe scan tool temperature is wrong but the engine temperature is normal

      It meansThe sensor or its circuit is at fault.

      Go to step 2

  2. With the key off, unplug the coolant sensor, turn the key on and see what the scan tool reads.

    Use cautionTool: scan tool, basic hand tools

    Warning:Do this only on a cold engine. Coolant and engine parts can be hot enough to burn.

  3. Ask a dealer whether your VIN has an open bulletin for P0117, particularly on Ford 2.7L EcoBoost engines.

    Low risk

Symptoms

  • Check engine light on
  • Cooling fans running all the time
  • Poor fuel economy or black exhaust smoke
  • Rough idle or stalling
  • Temperature gauge in the red or an over-temperature warning Gets more serious: stop and have it checked.

How to fix

  1. Check the coolant level when the engine is cold and top it up with the correct coolant if it is low.

  2. Look at the sensor connector for loose or corroded terminals.

Parts and cost context

  • Engine coolant temperature (ECT) sensor:The sensor is inexpensive and a common first fix once the wiring checks out. Labour varies by engine; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Dodge

  • 2011 · Journey

    Supported by vehicle data

    Chrysler bulletin 05-002-12 covers the MIL with P0117 or P0118 on the 2011 Journey. Whether the bulletin is still current is not verified.

  • 05-002-12Status unverified

    MIL on with P0117 or P0118

    2011journey · NHTSA 10044202

    Chrysler service information for a 2011 Journey with the MIL on for coolant temperature sensor circuit low or high. The NHTSA summary does not state the repair.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Ford

  • 2015–2020 · F-150

    Supported by vehicle data

    Ford SSM 48991 ties P0117 on 2.7L EcoBoost trucks to the coolant temperature sensor or knock sensor harness, with both sensors replaced. Whether the bulletin is still current is not verified.

  • SSM 48991Status unverified

    2.7L EcoBoost MIL or over-temperature warning with P0117 and related codes

    2015–2020f-150, edge, fusion · NHTSA 10177705

    May be due to the coolant temperature sensor or knock sensor wiring harness; the repair replaces the coolant temperature sensor and the knock sensor.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Cadillac

  • 2010 · CTS

    Supported by vehicle data

    GM bulletin PI-0067 says a chafed engine harness over the transmission bellhousing can set P0117 with other coolant sensor codes on the 2010 CTS. Whether the bulletin is still current is not verified.

  • PI-0067Status unverified

    Intermittent MIL, reduced engine power with P0116 to P0119

    2010cts · NHTSA 10034407

    May be caused by chafing of the engine wiring where the harness routes over the transmission bellhousing.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Chevrolet

  • P0118Engine coolant temperature sensor circuit high

    Other bank Supported by vehicle data

    P0118 is the high-voltage counterpart on the same coolant sensor circuit. Chrysler and GM bulletins and a Cruze owner report the two together.

  • P0128Engine coolant stays below thermostat temperature

    Same system Supported by vehicle data

    P0128 (coolant below thermostat temperature) appears with P0117 in Ford bulletin SSM 48991 for 2.7L EcoBoost engines.

All Engine cooling (thermostat) codes

P0117 questions

Can I keep driving with P0117?

Usually yes for a short time, but watch the temperature gauge. Stop if the engine really overheats.

Why are my fans running all the time?

The computer thinks the engine is extremely hot because of the sensor reading, so it keeps the fans on.

Sources and review

  1. P0117 trouble code overview — TroubleCodes.net
  2. Ford SSM 48991 (NHTSA 10177705): 2.7L EcoBoost MIL and engine over-temperature warning with P0117 and related codes — Ford Motor Company
  3. NHTSA complaint ODI 10980210: Chevrolet Cruze 2011, P0117 and P0118 with coolant sensor and housing replacement — NHTSA Office of Defects Investigation
  4. GM bulletin PI-0067 (NHTSA 10034407): 2010 CTS intermittent MIL with P0116-P0119 — General Motors
  5. Chrysler bulletin 05-002-12 (NHTSA 10044202): MIL on with P0117 or P0118 on 2011 Dodge Journey — Chrysler Group
Last reviewed
Written by
Saurabh K.
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