ECD SYSTEM, Diagnostic DTC:P1290

DTC Code DTC Name
P1290 Radiator / Engine Coolant Temperature Circuit

DESCRIPTION

The radiator side engine coolant temperature sensor senses the coolant temperature. A thermistor built into the sensor changes the resistance value according to the coolant temperature. The lower the coolant temperature, the greater the thermistor resistance value, and the higher the coolant temperature, the lower the thermistor resistance value (See Fig. 1). The radiator side engine coolant temperature sensor is connected to the ECM. The 5 V power source voltage in the ECM is applied to the radiator side engine coolant temperature sensor from the terminal RTHW via a resistor R. That is, the resistor R and the radiator side engine coolant temperature sensor are connected in series. When the resistance value of the radiator side engine coolant temperature sensor changes in accordance with changes in the coolant temperature, the potential at the terminal RTHW also changes. Based on this signal, the ECM increases the fuel injection volume to improve driveability during cold engine operation.

The radiator side engine coolant temperature sensor controls the radiator fan.

B007PGXE01
DTC No. DTC Detection Condition Trouble Area
P1290 Open or short in radiator side engine coolant temperature sensor circuit for 3 second or more.

  • Open or short in radiator side engine coolant temperature sensor circuit

  • Radiator side engine coolant temperature sensor

  • ECM

WIRING DIAGRAM

B007TQ0E12

INSPECTION PROCEDURE

Tech Tips

Read freeze frame data using the GTS. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, and other data from the time the malfunction occurred.

PROCEDURE


  1. INSPECT RADIATOR SIDE ENGINE COOLANT TEMPERATURE SENSOR


    1. B007UWGE06

      Measure the resistance according to the illustration.

      OK
      The resistance value is within the acceptable range shown in the illustration.

      Note

      If checking the radiator side engine coolant temperature sensor in the water, do not allow water to enter the terminals, and after checking, wipe off the sensor.


    NG

    REPLACE RADIATOR SIDE ENGINE COOLANT TEMPERATURE SENSOR

    OK

  2. CHECK HARNESS AND CONNECTOR (ECM - RADIATOR SIDE ENGINE COOLANT TEMPERATURE SENSOR)


    1. Disconnect the radiator side engine coolant temperature sensor connector.

    2. Disconnect the ECM connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      B29-2 - D100-68 (RTHW) Always Below 1 Ω
      B29-1 - D100-91 (EPEX) Always Below 1 Ω
      B29-2 or D100-68 (RTHW) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

    REPLACE ECM Click here