If it fails at one extreme, the temp sensor will cause the engine to run very rich all the time, not just at startup/warmup. At the other extreme, it will cause the engine to run very lean all the time. Of the two, lean is a more alarming condition as it could result in overheating, detonation, and engine damage.
If you have a simple multimeter, follow the test procedure in the FI troubleshooting guide. Don't be tempted to test resistance at the sensor's pigtail---rather, test it at the main harness connection to the Bosch FI control unit per the troubleshooting guide, as doing it that way not only tests the sensor but also tests the wiring to/from the control unit. The ground for the sensor's wiring is one of the two FI harness grounding eyelets on the cam box cover retaining studs.