Model: CC7000ZM01BEV, with a cruising range of 310km.
Driving Mileage: 14km.
Issue: After charging the battery overnight, the vehicle can be started the next day when preparing to wash the car for delivery, but after the D gear is engaged, the vehicle cannot drive, and the gear information displayed on the meter continues to flash at the N gear position, as shown in Figure 1.
Diagnosis: Combined with the fault phenomenon, analyze the possible causes: one is that the brake pedal is not fully depressed or the brake switch or wiring related to braking is abnormal; the other is the shift knob or related wiring is abnormal; the third is the Vehicle Control Unit (VCU) or KBCM and related lines are abnormal.
After asking the sales consultant about the situation, it was confirmed that the operation had no problem. Step on the brake pedal to start the vehicle and enter the READY mode, indicating that the brake-related switches and circuits were good, so that we eliminated the first possibility.
The second and third possibilities can be combined with the diagnostic instrument to read the related data stream or fault code. Read the fault code with a special diagnostic instrument and found that there are two current faults stored in the VCU, namely P103121 gear 1 voltage is too low and P103963 gear fault, and the gear status is all 0. The possible cause may be a problem between the related circuit of the shift knob and the controller. Check the maintenance manual. According to the maintenance instructions, there is nothing wrong in the basic direction. Now you need to measure on the actual vehicle.
Definition of fault code P1 0 3 9 6 3: gear fault.
Fault code condition: The gear switch is not in the R/N/D state.
Possible reasons for the failure: damage to the gear sensor or incorrect installation; damage to the vehicle controller.
Fault code elimination condition: the gear switch is in the R/N/D state.
The definition of fault code P103121: the voltage of gear 1 is too low.
Fault code condition: The voltage value of gear 1 is lower than 1.5V.
Possible causes of the fault: The gear 1 sensor connector is loose; the gear 1 sensor is short-circuited or disconnected to the ground; the gear 1 sensor is damaged or installed incorrectly; the vehicle controller is damaged.
Trouble code elimination condition: The voltage value of gear 1 is higher than 1.5V.
Check the circuit diagram and combine the first fault code to focus on the voltage output when the voltage of gear 1 is in different gears. When measuring the gear output, it is necessary to plug in the shift knob plug and measure at the rear, so the space is limited. According to the analysis of the circuit diagram, the output line must have a detection signal from the VCU to determine whether the line is open, grounded or short-circuited to the power supply. Measure the output signal line voltage of 2/3/4 block to be about 4.9V, and measure the voltage of pin 11 of output signal 1 to 0.1V, indicating that there is indeed an abnormality in this line. It may be that the circuit is grounded to the vehicle body or the vehicle controller (VCU) is grounded internally.
Without disconnecting the VCU connector, measure the resistance of pin 11 to ground to 1.9Ω, and the resistance of other signal output lines to 2.7kΩ; disconnect the VCU plug and measure the resistance of pin 11 to ∞ again, indicating that the VCU is short-circuited to ground. Because it was out of stock, the plug was restored and it was prepared to report to the warehouse for ordering. It was found that the vehicle could be driven in gear, and after observing for a period of time, the vehicle was not abnormal in use again.
Summary: The analysis shows that in addition to the logic gear input information and the judgment of the corresponding gear, the VCU will also detect these signal circuit lines to detect whether it is grounded, short-circuited or disconnected to the power supply. It may be that after fully charged, the current and voltage are abnormal, and the internal protection of the module is caused.