For a 2019 SAIC eMG6 hybrid new energy vehicle, the EP fault light on the dashboard is on, and the vehicle cannot be powered on or started (Figure 1). Read the fault information with a diagnostic instrument and read it in the hybrid control module HCU There is a fault code U010387-the communication with the shift control unit (SCU) is lost (Figure 2).
Check the shift control unit and find that the indicator light of this unit is not on (Figure 3). If you want to determine the cause of the failure, you must first understand the control principle of the shift control unit, and check it step by step according to the circuit diagram of the shift control unit. According to the maintenance manual, it is known that the shift control module includes the module, the shift lock solenoid valve, the rotation angle position sensor, the P gear micro switch and the gear display component (Figure 4). At the same time, the shift control module is still on the power high-speed CAN bus. In the network (Figure 5). The actual data exchange of the shift control module only involves the hybrid control module HCU, which mainly transmits the gear signal to the hybrid control module via high-speed CAN, while the P gear signal is transmitted to the body control module via hard wire. According to preliminary judgment, the cause of the failure may be the power supply failure of the shift control module SCU, poor grounding or bus short-circuit failure.
Next is simple, use a multimeter to measure the power supply lines BY054-1, BY054-2 and BY054-7 of the shift control module. When measuring the BY054-1 pin, it is found that there is no voltage. This pin is the power supply of ignition switch ON. The power supply comes from the F22 fuse of the body control module (Figure 6). After removing the F22 fuse, it was found that it had been blown. After replacing the F22 fuse, the fault of the car was completely eliminated.
In this case, although the malfunctioning car is a hybrid car, the malfunction of the car is not complicated at all. Because only by consulting the maintenance manual and analyzing the relevant circuit diagrams, you have a complete understanding of the control principle of the gear shift control module of the faulty model, and then through the measurement of the multimeter, you can accurately determine the location of the fault.
