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EngineModerate✅ DIY Friendly

P0118

Engine Coolant Temperature Circuit High Input

ECT sensor voltage is higher than expected — ECM thinks engine is very cold.

SeverityModerate
CategoryEngine
Est. Repair Cost$30–$200
Code TypePowertrain
DIY RepairYes

⚡ Common Causes

  • ›Open circuit in ECT wiring
  • ›Disconnected ECT sensor
  • ›Faulty sensor
  • ›Damaged wiring harness

⚠️ Symptoms

  • ›Engine runs rich when warm
  • ›Poor fuel economy
  • ›Heater may blow cold
  • ›Check engine light

✅ How to Fix — Step by Step

  • Step 1:Check ECT sensor connection
  • Step 2:Test wiring continuity
  • Step 3:Replace ECT sensor
  • Step 4:Inspect harness for damage

🔧 Diagnostic Tools Required

Using the correct diagnostic tools helps identify the root cause of P0118 before replacing parts unnecessarily. Always confirm the fault using live data and manufacturer-recommended diagnostic procedures.

💡 Pro Tip: Disconnect the ECT sensor — if the temperature gauge changes, the circuit is working but sensor is bad.

Repair Cost Estimate

Full Repair Estimate
$30–$200
DIY Possible?
YES
Severity
Moderate

Frequently Asked Questions

What does OBD2 code P0118 mean?+
P0118 stands for Engine Coolant Temperature Circuit High Input. ECT sensor voltage is higher than expected — ECM thinks engine is very cold.
What causes code P0118?+
Open circuit in ECT wiring; Disconnected ECT sensor; Faulty sensor; Damaged wiring harness
How do I fix code P0118?+
Check ECT sensor connection; Test wiring continuity; Replace ECT sensor; Inspect harness for damage
How much does it cost to fix P0118?+
Estimated repair cost for P0118 is $30–$200.
Is P0118 DIY-friendly?+
Yes — P0118 is generally DIY-friendly with basic tools.

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