P0181

DTC P0181

CIRCUIT DESCRIPTION
The fuel temperature sensor is a thermistor that measures the temperature of the fuel being returned to the fuel tank. The engine control module (ECM) supplies the fuel temperature sensor a reference voltage of 5 volts on the signal circuit and a ground for the low reference circuit. When the fuel temperatures are low, the resistance is high. The signal voltage remains near the supplied voltage cold and decreases as the sensor warms. The ECM uses a fuel temperature rationality test to determine if the fuel temperature input is inaccurate. The ECM will record the amount of time the engine is OFF. During cold start the ECM will calculate the temperature difference between the fuel temperature sensor and the intake air temperature (IAT). Before failing this diagnostic, the ECM will perform a calculation to determine the presence of a block heater. If this diagnostic fails, DTC P0181 sets.

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

CONDITIONS FOR RUNNING THE DTC
- DTCs P0112, P0113, P0182, P0183, P0500, or P2610 are not set.
- The engine is running.
- The engine must be OFF for 10 hours or more.
- The start-up intake air temperature (IAT) is more than 15°C (59°F).
- DTC P0181 runs once per drive cycle within the enabling conditions.

CONDITIONS FOR SETTING THE DTC
- The ECM detects the fuel temperature and the engine coolant temperature (ECT) are more than 9.75°C (18°F) of each other at start-up.
- The IAT has decreased less than 5.25°C (10°F) after the engine has been 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.

DIAGNOSTIC AIDS
- Ensure that an engine block heater or front grill blanket is not being used at temperatures above -17°C ( 0°F ).
- A engine block heater is used at temperatures above -17°C ( 0°F ) this DTC may set.
- A front grill blanket is used at temperatures above -17°C ( 0°F ) this DTC may set.
- If this DTC cannot be duplicated, the conditions may be intermittent. Refer to Intermittent Conditions. Diagnostic Strategies

TEST DESCRIPTION

Steps 1-3:

Steps 4-6:

Steps 7-8:

Steps 9-12:

Steps 13-17:

Steps 18-19:

The numbers below refer to the step numbers on the diagnostic table.
2. This step determines if the IAT sensor is within the normal range. If the value is outside of the specification, the IAT sensor may be inaccurate or the circuit may have high resistance.
4. This step determines if the fault is present at the time of diagnosis.
15. Reprogram the replacement ECM. Refer to the latest techline information for ECM programming.