P0168

CIRCUIT DESCRIPTION
The fuel temperature sensor is a thermistor type sensor. The Engine Control Module (ECM) supplies 5 volts and a ground circuit to the sensor. When the ECM detects a fuel temperature above a pre-determined value, a type C code, no Malfunction Indicator Lamp (MIL) sets. A fuel cooler located in front of the fuel tank is used to help keep the fuel temperature at an acceptable limit.

CONDITIONS FOR RUNNING THE DTC
The ignition is ON.

CONDITIONS FOR SETTING THE DTC
The fuel temperature is above 122 °C (252 °F) for more than 5 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Use a scan tool in order to clear the MIL and the DTC.

TEST DESCRIPTION

Steps 1-4:

Steps 5-13:

The numbers below refer to the step numbers on the diagnostic table.
2. This step checks for a problem in the fuel cooler that could cause the fuel temperature to increase above the pre-determined specification due to a lack of cooler efficiency.
5. This step checks for a voltage above or below the 5 volts supplied by the ECM.