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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 965 (Engine Controls Diagnosis - 6.6L (Lb7) (DTCS P0016 To P0236)) >> Diagnosis >> DTC P0181 >> Circuit Description

Circuit Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

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.

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