P0115 Toyota Tundra
Engine Coolant Temperature Sensor Circuit · Powertrain Code · Medium · Repair: Easy
What is P0115?
The engine coolant temperature sensor circuit has a fault — bad sensor, wiring, or connector.
When the Toyota Tundra triggers code P0115 (engine coolant temperature sensor circuit), it typically points to an issue in the powertrain system. Below you'll find the most common causes, symptoms, and repair options specific to the Toyota Tundra.
This repair is rated easy, meaning basic tools, no lift needed.
Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your Toyota Tundra.
Common Causes on Toyota Tundra
- Engine coolant temperature (ECT) sensor circuit malfunction
- Corroded ECT sensor connector near thermostat housing
- Failed Denso ECT sensor (common after 150k miles)
- Damaged wiring between ECT sensor and ECM
Symptoms
- Check Engine Light on
- Cooling fans may run continuously or not at all
- Inaccurate temperature gauge reading on dashboard
- Poor cold-start fuel mixture causing rough idle
- Higher than normal idle speed when engine is warm
Notes for Toyota Tundra
The ECT sensor is a $15 part and takes 10 minutes to replace on most Toyota engines — always replace rather than attempting to repair.