ECD SYSTEM, Diagnostic DTC:P0168/39

DTC Code DTC Name
P0168/39 Fuel Temperature Too High

DESCRIPTION

The fuel temperature sensor monitors the fuel temperature. The fuel temperature sensor has a thermistor that varies its resistance depending on the fuel temperature. When the fuel temperature is low, the resistance in the thermistor increases. When the temperature is high, the resistance decreases. The variations in resistance are communicated to the ECM as changes in voltage (see Fig. 1).

The fuel temperature sensor is connected to the ECM (see below). The 5 V power source voltage in the ECM is applied to the fuel temperature sensor from terminal THF via resistor R.

The resistor R and fuel temperature sensor are connected in series. When the resistance value of the fuel temperature sensor changes in accordance with changes in the fuel temperature, and the voltage at terminal THF also changes. Based on this signal, and the ECM corrects the pressure control compensation of the supply pump and errors.

A01BBBAE03
DTC No. DTC Detection Condition Trouble Area
P0168/39

  • If fuel temperature is between 35°C (95°F) and 60°C (140°F) at engine start, and conditions (a) and (b) are met:

    (2 trip detection logic)


    1. Vehicle is driven at varying speeds (under acceleration and deceleration)

    2. Fuel temperature remains within 3°C (5.4°F) of engine starting temperature

 Fuel temperature sensor
P0168/39

  • If fuel temperature is more than 60°C (140°F) at engine start, and conditions (a) and (b) are met:

    (6 trip detection logic)


    1. Vehicle is driven at varying speeds (under acceleration and deceleration)

    2. Fuel temperature remains within 1°C (1.8°F) of engine starting temperature, and this is continuously recorded 6 times

 Fuel temperature sensor

INSPECTION PROCEDURE

Tech Tips


  • If DTCs P0180/39, P0182/39 or P0183/39 is set simultaneously with P0168/39, the fuel temperature sensor may have an open or a short circuit. Troubleshoot those DTCs first.

  • Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, and other data from the time the malfunction occurred.

PROCEDURE


  1. CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC P0168/39)


    1. Connect an intelligent tester to the DLC3.

    2. Turn the ignition switch ON and turn the intelligent tester ON.

    3. Enter the following menus: Powertrain / Engine / DTC.

    4. Read the DTCs.

      Result
      Display (DTC Output) Proceed to
      P0168/39 A
      P0168/39 and other DTCs B

      Tech Tips

      If any DTCs other than P0168/39 are output, perform the troubleshooting for those codes first.


    B

    GO TO DTC CHART

    A

    REPLACE FUEL TEMPERATURE SENSOR