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P0115 — Engine Coolant Temperature Sensor 1 Circuit

What it means: Engine Coolant Temperature Sensor 1 Circuit.

How serious / can you keep driving: Caution. Limp to the next safe stop.

Check first: Measure ECT sensor resistance

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CautionCoolingLimp to the next safe stop

Seen on: Heavy Truck

What P0115 means

Engine Coolant Temperature Sensor 1 Circuit. Common causes: ECT sensor circuit fault.

How serious is it?

Caution. Limp to the next safe stop.

Most likely causes

  1. ECT sensor circuit fault
  2. Failed sensor
  3. wiring fault

First moves (roadside)

  1. Measure ECT sensor resistance
  2. check wiring
  3. replace sensor

FAQ

What does P0115 mean?

Engine Coolant Temperature Sensor 1 Circuit. Common causes: ECT sensor circuit fault.

How serious is P0115?

Caution — Limp to the next safe stop.

What's the most likely cause of P0115?

The most common cause is: ECT sensor circuit fault. Other possibilities include Failed sensor; wiring fault.

Can I keep driving with P0115?

Limp to the next safe stop. When in doubt, get a qualified mobile diesel tech on the truck before continuing.

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Related codes

Codes that commonly appear alongside P0115, or share the same subsystem.

Same symptom: Running hot

Other codes that show up as coolant temperature climbing or a hot-engine lamp.

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General diagnostic guidance for diesel engines (Cummins, Detroit, PACCAR, Volvo, Mack and more). Not a substitute for a scan-tool diagnosis on your specific truck.