P0181

CIRCUIT DESCRIPTION
The Fuel Temperature (FT) Sensor is a thermistor. The Engine Control Module (ECM) supplies the FT sensor a reference voltage of 5 volts on the signal circuit and also provides a low reference circuit to the sensor. When the FT sensor is cold, the resistance is high. The FT sensor signal voltage remains near the supplied voltage cold and decreases the signal voltage as the sensor warms. The control module monitors the FT sensor signal circuit in order to calculate the temperature of the fuel entering the engine.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0112, P0113, P0182, P0183, or P1683 are not set.
^ Engine must be turned OFF for 10 hours or longer.
^ Start-up Intake Air Temperature (IAT) is more than 10°C (50°F).
^ The fuel temperature and the IAT must be within 10°C (18°F) of each other at start-up.

CONDITIONS FOR SETTING THE DTC
The fuel temperature and the IAT are more than 10°C (18°F) of each other at start-up.

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 1-5:

Steps 6-15:

The numbers below refer to the step numbers on the diagnostic table.
2. This step determines if the IAT sensor reading is reading within a normal range. If the reading is outside of the specification, the IAT sensor may have a fault in the sensor or circuit.
3. This step determines if the fault is present at the time of diagnosis.
11. Reprogram the replacement ECM. Refer to the latest techline information for ECM programming.