Circuit/System Description

Fuel is drawn from the fuel tank through the fuel heater, then to the fuel injection pump. Fuel temperature is monitored by the fuel temperature sensor, which is located in the fuel return line on the engine. The engine control module (ECM) supplies 5 volts and a ground circuit to the sensor. When the ECM detects a fuel temperature above the pre-determined value, this diagnostic will fail, but will not turn the malfunction indicator lamp (MIL) ON.