Toyota Corolla (E120): Circuit description

Refer to dtc p0115

Dtc no.

Dtc detection condition

Trouble area

P0125 If the engine coolant temperature (ect) was less than –6.6 °C (20 °F) when starting the engine, and 20 minutes after the engine start, the ect sensor still indicates below 20 °C (68 °F)
  • Cooling system
  • engine coolant temperature sensor
  • thermostat
If the ect was between –6.6 °C (20 °F) and 10 °C (50 °F) when start, 5 minutes after the start, the ect sensor still indicates below 20 °C (68 °F)
If the ect was greater than 10 °C (50 °F) when starting the engine, and 2 minutes after the engine start, ect sensor still indicates below 20 °C (68 °F)

Monitor description

The engine coolant temperature (ect) sensor is used to monitor the temperature of the engine coolant. The resistance of the sensor varies with the actual coolant temperature. The ecm applies a voltage to the sensor and the varying resistance of the sensor causes the signal voltage to vary. The ecm monitors the ect signal voltage after engine start–up. If, after sufficient time has passed, the sensor still reports that the engine is not warm enough for closed–loop fuel control, the ecm interprets this as a fault in the sensor or cooling system.

Example: the engine coolant temperature was 0 c (32 f) at engine start. After 5 minutes running time, the coolant temperature sensor still indicates that the engine is not warm enough to begin air–fuel ratio feedback control.

The ecm interprets this as a fault in the sensor or cooling system and will set a dtc.

Monitor strategy

Typical enabling conditions

Typical enabling conditions

Typical malfunction thresholds

Typical malfunction thresholds

Wiring diagram

Wiring diagram

Refer to dtc p0115

    Share this page:

    Other materials:

    Adjustment
    1. Inspect park/neutral position switch assy  apply the parking brake and turn the ignition switch on.  depress the brake pedal and check that the engine starts only when the shift lever is set in n or p position and it does not start in the other position.  check that th ...

    Diagnostic trouble code chart
    Notice: when removing the part, turn the ignition switch to off. Hint: using sst 09843–18040, it connect the terminal tc and cg of dlc3. If any abnormality is not found when inspecting parts, inspect the ecu and ground points for poor contact. If a malfunction code is displayed during ...

    Inspection procedure
    1 Prepare for inspection Disconnect the negative (–) terminal cable from the battery, and wait at least for 90 seconds.  remove the horn button assy .  disconnect the connector of the instrument panel passenger airbag assy .  disconnect the connector of the front sea ...