Field Effect Transistor (FET) Protection

The GFM2 uses field effect transistors (FETs) to control module outputs. the GFM2 monitors output loads for excessive current (typically short circuits). When a fault event is detected, the GFM2 turns the FET off, a short circuit DTC is set and a cumulative fault event counter is started. The module resets the FET protection and allows the circuit to function when the fault is corrected and the DTC is cleared. The module never resets the fault event counter and continues to advance the fault event counter as short circuit fault events occur. If the number of short circuit fault events reaches a predetermined level, DTC U1000:00 sets along with the associated short circuit DTC. The module never resets the fault event counter to zero and continues to advance the fault event counter as short circuit fault events occur. When the fault event counter reaches another predetermined level, DTC U3000:49 sets along with the associated short circuit DTC. DTC U3000:49 cannot be cleared and the module must be replaced after the initial fault is repaired.