MechanicDB
Home / Diagnostic Decoder / Powertrain System / Code P0118
System: Powertrain (P-Code) Coverage: SAE Standard (Generic) Fault Family: ect_sensor_circuit

Code P0118: Engine Coolant Temperature Sensor 1 Circuit High

Diagnostic & Technical Explanation
Code P0118 (Engine Coolant Temperature Sensor 1 Circuit High) sets when the ECM sees an open, shorted, or implausible resistance from an engine or radiator coolant temperature sensor, or a correlation mismatch between redundant coolant/oil/ambient temperature signals. Causes are a corroded connector, a failed thermistor element, low coolant exposing the sensor tip, or chafed wiring.

Probability-Ranked Repair Procedures (3 Ranked Fixes)

Rank #1

Top off coolant and inspect ECT sensor connector

Easy DIY
Parts Estimate: $10.0–$30.0 USD Labor Estimate: 0.4 Shop Hours
  1. 1. Check coolant level and top off with the correct spec coolant
  2. 2. Unplug the ECT sensor connector and inspect for corrosion
  3. 3. Clean contacts and reconnect
  4. 4. Clear codes and monitor warm-up temperature curve
Required Replacement Parts: 🔧 Coolant (OEM-spec type)
Rank #2

Replace engine/radiator coolant temperature sensor

Moderate DIY
Parts Estimate: $15.0–$70.0 USD Labor Estimate: 0.6 Shop Hours
  1. 1. Relieve cooling system pressure and drain coolant to below sensor level
  2. 2. Remove the sensor from the head, housing, or radiator tank
  3. 3. Install the replacement sensor with sealant or new seal as specified
  4. 4. Refill coolant, bleed air, and clear codes
Required Replacement Parts: 🔧 Coolant temperature sensor · 🔧 Coolant (OEM-spec type)
Rank #3

Repair coolant temperature sensor wiring

Professional Required
Parts Estimate: $10.0–$60.0 USD Labor Estimate: 1.2 Shop Hours
  1. 1. Measure sensor resistance at the connector against a temperature/resistance chart
  2. 2. Voltage-drop test the circuit back to the ECM
  3. 3. Repair chafed or corroded wiring with heat-shrink splices
  4. 4. Confirm reading tracks actual coolant temperature
Required Replacement Parts: 🔧 Automotive wiring repair kit (solder + heat-shrink)

Need All 15,886 OBD-II Codes & 56,561 Fixes?

Download the complete commercial MechanicDB dataset instantly. Includes CSV, Apache Parquet tables, and a relational SQLite database with commercial application rights.

License Full Dataset · Instant Download ($49)