P0181

DTC P0181

CIRCUIT DESCRIPTION
The fuel temperature (FT) sensor is a variable resistor. The FT sensor has a signal circuit and a low reference circuit. The FT sensor measures the fuel temperature of the fuel. The engine control module (ECM) supplies 5 volts to the FT signal circuit and a ground for the FT low reference circuit. When the FT sensor is cold, the sensor resistance is high. When the fuel temperature increases, the sensor resistance decreases. With high sensor resistance, the ECM detects a high voltage on the FT signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the FT signal circuit. If the ECM detects a difference of fuel temperature smaller than the calculated range during the predetermined engine run time, this DTC will set.

Condition for Running the DTC
- DTCs P0016, P0116, P0117, P0118, P0182, P0183, P0201, P0202, P0203, P0204, P0261, P0264, P0267, P0270, P0234, P0299, P0300, P0301, P0302, P0303, P0304, P0335, P0336, P0500, P0602, P0642, P0643, P1293, P2146, P2147, P2148, P2149, P2150 and P2151 are not set.
- The battery voltage is between 10-16 volts.
- The ignition switch is ON.
- The engine is running.
- The engine coolant temperature (ECT) is more than 140 °F (60 °C).
- The engine run time is between 100 seconds and 840 seconds.
- The fuel burned since startup is more than 390000 cu.mm.
- The vehicle speed is higher than 16 MPH (25 km/h).

Condition for Setting the DTC
- The ECM detects that the difference of maximum FT and minimum FT is less than 1.8 °F (1 °C).

Action Taken When the DTC Sets
- The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Freeze Frame/Failure Records.
- The ECM limits fuel injection quantity within 50%.
- The ECM limits fuel rail pressure within 11600 psi (80MPa)
- The ECM closes the EGR valve and holds to close position.
- The ECM inhibits the cruise control.

Condition for Clearing the MIL/DTC
- The ECM turns OFF the MIL after 3 consecutive driving cycles when 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 after the ECM turns OFF the MIL.
- Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
If an intermittent condition is suspected, the following may cause an intermittent:
- Damaged harness: inspect the wiring harness for damage. If the harness appears to be OK, observe the "FT Sensor" display on the scan tool with the engine running while moving connectors and the wiring harness related to the sensor. A change in the display will indicate the location of the fault.

Test Description
The number below refers to the step number on the diagnostic table.
2. This step tests for excessive resistance in the FT sensor circuit.

DTC P0181
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Connector End Views or Engine Control Module (ECM) Connector End Views

Step 2 - 6:

Step 7 - 10: