P0181

DTC P0181

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

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P0181 Fuel Temperature Sensor Performance

CONDITIONS FOR RUNNING THE DTC
- DTC P0112, P0113, P0182, P0183, P0500, P2610 are not set.
- The engine must be turned OFF for 10 hours or longer.
- The start-up intake air temperature (IAT) is more than 15°C (59°F).
- DTC P0181 will only run once per ignition cycle until a Pass, Fail, or Disable conditions exists.

CONDITIONS FOR SETTING THE DTC
- The fuel temperature and the ECT are more than 9.75°C (18°F) of each other at start-up.
- The IAT has dropped less than 5.25°C (10°F) after running more than 400 seconds above 24 km/h (15 mph).

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.
- Clear the MIL and the DTC with a scan tool.

TEST DESCRIPTION

Steps 1-10:

Steps 11-17:

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.
13. Reprogram the replacement ECM. Refer to the latest techline information for ECM programming.