Troubleshooting

P0115 - Engine Coolant Temp Circuit Malfunction

CIRCUIT DESCRIPTION

DTC Detecting Condition:

A thermistor built into the water temperature. sensor changes the resistance value according to the water temperature.
The structure of the sensor and connection to the engine ECM is the same as the ones of the air temperature sensor.

Wiring Diagram:

Step 1 - 3:

Step 4 - 5:

INSPECTION PROCEDURE

HINT:
- If DTC P0110 (Intake Air Temp. Circuit Malfunction), P0115 (Water Temp. Circuit Malfunction), P0120 (Throttle/Pedal Position Sensor/Switch "A" Malfunction) are output simultaneously, E1, E2 etc. (Sensor Ground system) may be open.
- Read freeze frame data using hand-held tester. Because freeze frame records the engine conditions when the malfunction is detected, when troubleshooting it is useful for determining whether the vehicle was running or stopped, the engine warmed up or not, the air-fuel ratio lean or rich, etc. at the time of the malfunction.

CHECK FOR INTERMITTENT PROBLEMS
TOYOTA hand-held tester only:
By putting the vehicle's ECM in the 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.
1. Clear the DTC
2. Set the check mode
3. Perform a simulation test.
4. Check the connector and terminal.
5. Handle the connector.