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All codes › P0118 › 2017 Ram 1500

P0118 on a 2017 Ram 1500

Coolant Temp Sensor High Input

Severity: moderate Safe to drive (short term) Pickup Truck 2015-2019 Ram 1500

What does P0118 mean on a 2017 Ram 1500?

P0118 is set when the engine control module reads the engine coolant temperature sensor signal voltage above the calibrated maximum — typically a reading that would represent an unrealistically cold coolant temperature (often −40 °F / −40 °C). This is the open-circuit fingerprint for the ECT sensor: a disconnected sensor, a broken signal wire, or a sensor failed open internally.

Symptoms on a 2017 Ram 1500

Likely causes on a 2017 Ram 1500

  1. Disconnected or unlatched ECT sensor connector Most common
    Estimated repair: $0– $50
  2. Broken or chafed ECT signal wire (open circuit) Common
    Estimated repair: $80– $350
  3. Internally failed ECT sensor (element opened) Common
    Estimated repair: $30– $200
  4. Corroded sensor connector pins Common
    Estimated repair: $30– $200
  5. Damaged sensor body from coolant leak or freeze Occasional
    Estimated repair: $50– $250
  6. Failed PCM signal input (rare) Rare
    Estimated repair: $400– $1,500

How to diagnose this on a 2017 Ram 1500

  1. Read ECT temperature with a scan tool

    A working ECT reads close to ambient air temperature when the engine has been off long enough to cool. A reading of "−40 °F" or "−40 °C" is the classic open-circuit fingerprint.

    Tools: Scan tool with ECT PID

  2. Inspect the connector and visible wiring

    Locate the ECT sensor (usually threaded into the intake manifold or thermostat housing). Unplug, inspect for corrosion, water, bent pins. Re-seat and clear the code — if it stays clear, the connector was the problem.

    Tools: Electrical contact cleaner, Flashlight

  3. Bench-test the ECT sensor resistance

    Remove the sensor (place a rag — coolant will drip). Measure resistance across its terminals at room temperature. Compare to the service manual — most NTC ECTs read 2.0–4.5 kΩ at 68 °F (20 °C). Infinite resistance means the sensor is open and needs replacement.

    Tools: Multimeter, Service spec sheet, Coolant catch and replacement

  4. Verify signal-wire continuity to the PCM

    With the ECT disconnected, check continuity from the sensor's signal wire to the corresponding PCM pin. Open circuit confirms a broken wire somewhere along the path. Visual inspection of the harness — particularly where it routes near hot exhaust or moving accessories — often reveals the chafe point.

    Tools: Multimeter, Wiring diagram

  5. Jumper-test the signal wire

    With the ECT disconnected, briefly jumper the signal wire to ground and observe the scan tool — the reading should swing from "very cold" to "very hot." No swing points at the wiring or PCM input rather than the sensor.

    Tools: Jumper wire, Scan tool

Common fixes

About the 2015-2019 Ram 1500

The 2015-2019 Ram 1500 was commonly sold with the following powertrains: 5.7L HEMI V8, 3.6L V6, 3.0L EcoDiesel V6. Common trims include Tradesman, Big Horn, Laramie, Rebel, Limited.

P0118 vs P0117

These are the two ends of the same circuit:

Why P0118 causes a hot engine to run rich

When the ECT signal goes missing or reads “very cold,” the ECM commands cold-start enrichment continuously — even on a hot engine. The result: fouled spark plugs, rich-running symptoms, possibly a hard start when the engine is actually warm because flooding occurs. This is why P0118 is worth fixing promptly even though it doesn’t look like a serious code.

Multi-sensor confusion: ECT vs IAT vs CHT

Modern engines may have multiple temperature sensors:

Their codes are similar — P0118 (ECT high), P0113 (IAT high), P0119 (ECT erratic). Make sure the connector you are pulling is for the sensor referenced in the code.

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