Both temperature sensors work by changing resistance as the temperature changes. If you have an ohm meter and therometer, proper functioning can be checked. Place the tip of the therometer and the tip of the sensor in a pan of cold water on the stove with the burner on. Connect the ohm meter across the sensor and plot resistance versus temperature as the water heats up. In cold water, the resistance should read 200-400 ohms and at 200 degrees F it should read 3000-4000 ohms. The temp sensor for the fuel injection has a fancy connector commpare to the one for the gauge. The fuel injection temp sensor is connected to pin no. 2 of the ECU connector. If you don't want to drain the coolant and pull the sensor, disconnect the ECU plug when the engine is cold and measure the resistance from pin 2 to ground. Do the same thing with the engine luke warm and hot and see if the resistance is changing. Pin 2 is the second pin down from the end where the cable enters the connector on the long side (the side with 13 pins). jp