P0118 Engine coolant temperature sensor circuit high

Coolant temperature sensor circuit high (reads too cold)

Severity not verified — if the car runs badly, have it inspected

Bulletins show P0118 ranging from no driveability symptoms (2001 Ford Focus) to a reduced engine power message (2010 Cadillac CTS) and a coolant over-temperature warning (Ford 2.7L EcoBoost), and we found no source that sets a general severity, so we have not rated it.

It gets more serious if:

  • Stop: The temperature gauge reaches the red, an engine coolant temperature high or overheat warning appears, you see steam from under the hood, or the engine loses power

Source: how we rate severity

P0118 in short

P0118 means the signal from the engine coolant temperature sensor is above its normal range, which usually looks like an extremely cold or unplugged sensor. Check the connector and wiring before replacing the sensor. Get it diagnosed, and stop at once if the temperature gauge reaches the red.

The coolant temperature sensor tells the engine computer how warm the engine is. The computer checks its circuit for breaks and readings out of range, and sets P0118 when the signal is stuck at the high end, which normally means the computer sees an impossibly cold engine.

A loose connector, damaged wiring or a failed sensor are the usual suspects. Ford had several bulletins for this on its 2.7L EcoBoost engines, and one tells technicians not to replace the sensor if the wiring is damaged.

How the car behaves varies. Some cars show nothing but the light, while others show a reduced power message or a coolant over-temperature warning. Treat a temperature warning as real until a technician proves otherwise.

Most likely causes

  1. ECT connector not fully seated, or damaged wiring

    Common general cause
    Why it ranks here
    The code checks the sensor circuit, so a loose or broken connection is a prime suspect, and Ford tells technicians to fix the wiring rather than the sensor when it is damaged.
    What would change this
    Rises if the connector is loose or the reading jumps when the wiring is moved. Falls if the circuit checks out.
    How to test the engine coolant temperature (ect) sensor

  2. Failed coolant temperature sensor

    Possible — needs testing
    Why it ranks here
    Ford replaces the ECT sensor on some 2.7L engines, but only after the wiring has been ruled out.
    What would change this
    Rises if the wiring and connector test good and the sensor reads wrong.
    How to test the engine coolant temperature (ect) sensor

  3. Engine harness chafed away from the sensor (2010 Cadillac CTS)

    Supported by vehicle data
    Why it ranks here
    GM traced P0116–P0119 with a reduced power message to wiring chafing on the transmission bellhousing.
    What would change this
    Rises on a 2010 CTS with this code, especially with a reduced power message.

  4. Intermittent ECT voltage drop needing the relocated sensor (2018–2020 F-150 2.7L)

    Supported by vehicle data
    Why it ranks here
    Ford fixes an intermittent ECT signal drop on these trucks with a heater hose carrying a relocated sensor and a jumper harness.
    What would change this
    Rises on a covered F-150 with an intermittent code or a coolant over-temperature warning.
    How to test the engine coolant temperature (ect) sensor

What to test first

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

  1. With the engine cold after sitting overnight, read the coolant temperature on a scan tool and compare it with the outside temperature.

    Low riskTool: OBD-II scan tool with live data

    • IfIt shows an extremely low value that does not change as the engine warms

      It meansThe signal is stuck at the high end. Check for a bulletin, then the connector.

      Go to step 2

    • IfIt reads sensibly and the code comes and goes

      It meansAn intermittent connection is likely. Check for a bulletin.

      Go to step 2

  2. Check for an ECT bulletin for your VIN at a dealer or on the NHTSA site.

    Low risk

  3. Have a technician check that the ECT connector is fully seated and test the wiring back to the engine computer.

    Best left to a shopTool: multimeter, wiring diagram

    Warning:Work only on a cold engine. The sensor sits in the cooling system, and hot coolant can burn.

Symptoms

  • Check engine light, sometimes with no other symptom
  • Reduced engine power message on some vehicles
  • Temperature gauge reading cold or not moving
  • Engine coolant over-temperature warning, red gauge or steam Gets more serious: stop and have it checked.

Compare with: Check engine light with loss of power

How to fix

  1. Do not replace the sensor on the code alone. Have the connector and wiring checked first.

  2. Ask a dealer whether your VIN has an open ECT bulletin. Ford has several for its 2.7L EcoBoost.

  3. If a coolant temperature warning appears or the gauge reaches the red, pull over safely and switch off.

    Warning:Never open the radiator cap or coolant reservoir cap while the engine is hot. Hot coolant and steam can spray out and burn you. Check only with the engine fully cold.

Parts and cost context

  • Engine coolant temperature (ECT) sensor:Replace only after the connector and wiring test good. On some Ford 2.7L engines the fix is a harness or a relocated sensor.

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

Compare used part prices on PartPriceGuide

On your vehicle

Ford

  • 2015–2020 · F-150 · 2.7L EcoBoost

    Supported by vehicle data

    Ford has three messages for P0118 and related ECT codes on the 2.7L: an unseated connector or damaged wiring (SSM 47791), the sensor or knock sensor harness (SSM 48991), and on 2018–2020 trucks an intermittent voltage drop fixed with a relocated sensor (TSB 21-2168). Some show a coolant over-temperature warning. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.

    Where it is:ECT sensor connector and harness

  • 2015–2020 · Edge · 2.7L EcoBoost

    Supported by vehicle data

    Ford SSMs 47791 and 48991 cover ECT codes including P0118 on the 2.7L Edge, plus Fusion, Lincoln MKX, Nautilus and Continental: check the connector and wiring first, then the sensor and harness. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.

    Where it is:ECT sensor connector and harness

  • 2001 · Focus

    Supported by vehicle data

    Ford bulletin 01113 covers a check engine light with P0118 and no driveability symptoms on Focus models built before 9 January 2001. The flat-file summary does not give the cause. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.

  • SSM 47791Status unverified

    ECT sensor codes from an ECT connector not fully seated or damaged wiring

    2015–2019f-150, edge, fusion · 2.7L · issued · NHTSA 10155563

    Lists P0116–P0119 and other codes on 2.7L engines. Check that the ECT sensor connector is fully seated and look for damaged wiring between the named connectors, and do not replace the sensor if the wiring is damaged. Lincoln MKX, Nautilus and Continental are also covered. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

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

  • SSM 48991Status unverified

    MIL and/or Engine Coolant Over Temperature warning with ECT and related codes

    2015–2020f-150, edge, fusion · 2.7L EcoBoost · issued · NHTSA 10177705

    Lists P0116–P0119, P0128, P0217 and others on 2.7L EcoBoost engines, due to the ECT sensor or knock sensor wiring harness. Replace the ECT sensor and the knock sensor harness. Lincoln MKX, Nautilus and Continental are also covered. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

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

  • TSB 21-2168Status unverified

    MIL and/or Engine Coolant Over Temperature warning from an intermittent drop in ECT voltage

    2018–2020f-150 · 2.7L EcoBoost · issued · NHTSA 10198582

    Lists P0116–P0119, P0128, P0217 and others. Fit the new heater hose with the relocated ECT sensor and a jumper harness. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

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

  • 01113Status unverified

    MIL with P0118 and no driveability symptoms

    2001focus · issued · NHTSA 618088

    Covers 2001 Focus models built before 9 January 2001 that show a check engine light with P0118 and no driveability symptoms. The flat-file summary does not give the cause or repair. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    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 PI-0067 traces P0116–P0119 with a reduced engine power message to engine wiring chafing over the transmission bellhousing. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.

    Where it is:Engine harness over the transmission bellhousing

  • PI-0067Status unverified

    Intermittent MIL and reduced engine power message with P0116–P0119 from harness chafing

    2010cts · issued · NHTSA 10034407

    Engine wiring can chafe where it runs over the transmission bellhousing and set coolant temperature sensor codes, with a reduced engine power message. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

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

  • P0128Engine coolant stays below thermostat temperature

    Shares causes Supported by vehicle data

    Ford lists P0118 and the warm-up code P0128 together on 2.7L EcoBoost engines with ECT sensor or wiring faults, so a bad ECT signal can set both.

  • P0217The engine computer has detected an engine over-temperature condition

    Shares causes Supported by vehicle data

    Ford lists P0118 with P0217 on 2.7L EcoBoost engines when the coolant temperature sensor or its wiring gives a false reading. Treat an over-temperature warning as real until proven otherwise.

  • P1299Ford and Lincoln: cylinder head over-temperature protection is active (the engine computer's fail-safe cooling mode)

    Shares causes Supported by vehicle data

    On 2.7L EcoBoost engines Ford lists P0118 with P1299 when coolant temperature sensor wiring gives a false hot reading.

  • P0125Coolant too cold for closed-loop fuel control

    Shares causes Possible — needs testing

    Both depend on the coolant temperature sensor. P0118 means its signal is stuck at the cold end, and a sensor reading low can make a warm engine look cold and set the warm-up code P0125.

All Engine cooling (thermostat) codes

P0118 questions

Is it safe to drive with P0118?

We have not rated it, because cars behave differently. Some show only the light, others a reduced power message or a coolant over-temperature warning. Get it diagnosed, and stop if the gauge reaches the red.

Should I replace the coolant temperature sensor?

Not first. The code is about the sensor circuit, and Ford tells technicians not to replace the sensor when the wiring is damaged. Check the connector and wiring before buying a sensor.

Why does my car show an overheat warning with P0118?

On some Ford 2.7L engines a faulty ECT signal can trigger the coolant over-temperature warning. Do not assume it is false: pull over safely, switch off and have it checked.

Sources and review

  1. Ford 01113: MIL with P0118 and no driveability symptoms, early-build 2001 Focus — Ford Motor Company / NHTSA ,
  2. GM PI-0067: MIL and reduced engine power with P0116–P0119 from harness chafing at the bellhousing, 2010 Cadillac CTS — General Motors / NHTSA ,
  3. Ford SSM 48991: MIL and/or Engine Coolant Over Temperature warning with ECT codes on 2.7L EcoBoost — Ford Motor Company / NHTSA ,
  4. Cal. Code Regs. Tit. 13, § 1968.2 — Malfunction and Diagnostic System Requirements (OBD II) — California Air Resources Board (via Cornell LII)
  5. Toyota Camry Owner's Manual (OM06291U, 2.5L A25A-FKS / 3.5L 2GR-FKS) — Toyota
  6. Ford SSM 47791: ECT sensor codes on 2.7L engines from an unseated ECT connector or damaged wiring — Ford Motor Company / NHTSA ,
  7. Ford TSB 21-2168: MIL and/or Engine Coolant Over Temperature warning from an intermittent ECT voltage drop, 2018–2020 F-150 2.7L — Ford Motor Company / NHTSA ,
  8. Ford SSM 48991: MIL and/or Engine Coolant Over Temperature warning from the ECT or knock sensor harness, 2.7L EcoBoost — Ford Motor Company / NHTSA ,
  9. Ford TSB 21-2168: MIL and/or Engine Coolant Over Temperature warning from an intermittent ECT voltage drop — Ford Motor Company / NHTSA ,
Last reviewed
Written by
Saurabh K.
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