Symptom: Santana car automatic transmission shift lever in the run without step on the brake pedal can switch between any gears.
    Troubleshooting: The car configuration 01N four-speed automatic transmission, with a fault diagnosis V. A. G1552 query automatic transmission control unit without fault code, with a multimeter to measure the shift lever lock solenoid valve resistance and the new solenoid valve the same. And then measure the voltage at both ends, when not on the brake pedal when 0V, press the brake plate is also OV. The solenoid valve is controlled by the transmission control unit via the transmission control unit. When the brake pedal when the brake switch F closed from the battery positive to the 30th power supply through the brake switch F is divided into two, all the way to the brake light power supply, the brake light, the other way to the transmission control unit Brake pedal depress the signal, so that it sucks the shift solenoid valve, so that the solenoid valve from the P block to 1 block between any switch.
    Then check the brake switch F, when depressing the brake pedal when the two brake lights are not lit, only the high brake light, and not step on the brake pedal high brake light on the high light. First check the brake light, found the filament has been blown, replace the two bulbs. Miracle happened, the previous failure has disappeared.
    In order to find the root of the problem. Remove the two brake light bulbs first. And then measured with the brake switch F connected to the transmission control unit terminal 15 feet of the voltage-related circuit, the voltage is 56V, then the high brake light is bright. And then cut off the 15th foot related to another line, that is, ABs control unit to the brake light switch line, 15 feet of the voltage is still 5.6V. Now the problem is concentrated in the transmission control unit, just have a car with the type of car into the factory, the two brake light bulb off, the same failure also occurred in the car. This verifies that the vehicle's transmission control unit design is defective.
    When the two brake lights are in good condition, the current from the inside of the transmission control unit, that is, 15 feet, is routed through the two filaments. When the two filaments are blown, the current from the inside of the control unit passes through the light-emitting diode of the high brake light Light-emitting diode micro-bright), so that the 15 feet have a voltage of 5.6V, so that the control unit mistaken for the brake switch closed. So that the shift lever lock solenoid valve pull, shift lever in the unlocked state.
    Fault Summary: The model car there are such problems, indicating that the factory design is not thoughtful, I hope you peer in the future work of attention to this model, to avoid detours.