P0115

Schematic:

The Engine Coolant Temperature (ECT) sensor is a thermistor that is located in the lower coolant passage of the engine cylinder's head. The ECM monitors the voltage drop across the resistor as it varies with the resistance of the sensor. This sensor is used for fuel/ignition control, hot/low coolant light, coolant gage, and fan. A low voltage indicates a high temperature and vice-versa. The ECM sets this DTC if the engine temperature does not reach 37°C (99°F) within a specified time(varies with engine starting temperature).

DTC PARAMETERS
The engine temperature should be sufficiently high to switch over to closed loop after the engine has been running between 2 and 5 minutes.

DTC P0115 is a (type B) DTC

IMPORTANT: The ECT signal is continuously checked when ignition is On.

CAUTION: To avoid the danger of being burned, do not remove the coolant surge tank cap while the engine, radiator, and tank are hot: scalding fluid and steam can be blown out under pressure.

DIAGNOSTIC AIDS
DTC P0115 indicates a lower than normal engine coolant temperature and probably does not indicate a faulty ECT subsystem.

Possible causes:
^ Thermostat stuck open
^ Cooling fan always On
^ Corrosion in connector or resistance in wiring
^ Very low ambient temperature
^ ECT sensor

Start engine and observe ECT reading on Scan tool. Under normal conditions, it should rise smoothly to 88°C (190°F).

ECT may be compared to IAT with Scan tool if engine has cooled overnight. They should be within four degrees of each other with the ignition On and engine Off.