Troubleshooting

DTC P0115 Engine Coolant Temperature Circuit

CIRCUIT DESCRIPTION

DTC Detection Condition:

A thermistor built in the engine coolant temperature sensor changes the resistance value according to the engine coolant temperature.

The structure of the sensor and connection to the ECM is the same as those of the intake air temperature.

HINT: If the ECM detects the DTC P0115, P0117 or P0118, it operates the fail-safe functions in which the engine coolant temperature is assumed to be 80 °C (176 °F)

HINT: After confirming DTC P0115, P0117 or P0118, use the hand-held tester or the OBD II scan tool to confirm the engine coolant temperature in "DIAGNOSIS/ENHANCED OBD II/DATA LIST/ALL".

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

Component Operating Range:

The engine coolant temperature (ECT) sensor is used to monitor the engine coolant temperature. The ECT sensor has a thermistor that varies its resistance depending on the temperature of the engine coolant. When the coolant temperature is low, the resistance in the thermistor increases. When the temperature is high, the resistance drops. The variations in resistance are reflected in the voltage output from the sensor. The ECM monitors the sensor voltage and uses this value to calculate the engine coolant temperature. When the sensor output voltage deviates from the normal operating range, the ECM interprets this as a fault in the ECT sensor and sets a DTC.

Example:
When the ECM calculates that the ECT is -40 °C (-40 °F), or more than 140 °C (284 °F) and if either condition continues for 0.5 seconds or more, the ECM will set a DTC.

Wiring Diagram:

Step 1:

Step 2 - 3:

Step 3 (Continued) - 4:

Step 5:

INSPECTION PROCEDURE

HINT:
- If DTCs related to a different system that have terminal E2 as the ground terminal are output simultaneously, terminal E2 may have an open circuit.
- Read freeze frame data using the hand-held tester or the OBD II scan tool. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

CHECK FOR INTERMITTENT PROBLEMS

HINT:
Hand-held tester only:
By putting the vehicle's ECM in check mode, 1 trip detection logic is possible instead of 2 trip detection logic and sensitivity to detect open circuits is increased. This makes it easier to detect intermittent problems.

a. Clear the DTCs.
b. Switch normal mode to check mode.
c. Perform a simulation test.
d. Check the connector(s) and terminal(s).
e. Wiggle the harness connector(s).