Failure phenomenon
A 2014 Maserati Ghibli with a 3.0T engine has accumulated approximately 74,000 miles. The owner reported that the driver's side window could not be raised after being lowered to the bottom.
Fault Diagnostics
After receiving the car from the garage and test driving it, the driver's side window glass lift switch was operated.The left front glass lifter does not work, the other three windows are normal. With the fault detector test, found that the driver's side door control module (DDM) stored in a number of fault codes (Figure 1), suggesting that the message points to the DDM internal fault.
Fig. 1 Fault codes stored in DDM
View the relevant circuit (Figure 2) that the driver's side window glass lifter assembly directly controlled by the DDM; driver's side window glass lifter assembly (including lifting motor and position sensor) terminal 1 and terminal 4 for the driver's side window glass lifter motor control terminal, responsible for controlling the motor forward and reverse; terminal 2, terminal 3 and terminal 6 for the motor position (that is, on behalf of the window glass position) sensor terminal, where terminal 3 for the power supply (12V) terminal, terminal 6 for the lap terminal, terminal 2 for the position signal terminal. Terminal 2, Terminal 3 and Terminal 6 are the motor position (i.e. representing the position of the window glass) sensor terminals, of which Terminal 3 is the power supply (12V) terminal, Terminal 6 is the lap terminal and Terminal 2 is the position signal terminal.
Fig. 2 Driver's Side Window Lifting Control Circuit
Using a Pico oscilloscope to measure the waveform of the signal related to the driver's side window glass up/down control (Figure 4) from wire connector D014 (Figure 3), it was found that when the ignition switch was turned on, the voltage on terminal 20 of wire connector D014 was always about 12V, which was abnormal.
Fig. 3 Wire Connector D014
Fig. 4 Signal waveforms of window glass up/down control on the driver's side of the malfunctioning vehicle
Under normal conditions, the DDM does not control the driver's side window glass lift motor when the driver's side window glass lift switch is not operated, so the voltage on both terminals 20 and 10 of lead connector D014 should be 0V.It can be deduced that the DDM is damaged and continues to output 12V power, or the wire connected to terminal 20 of lead connector D014 is shorted to the power supply.
Disconnect the DDM lead connector G and measure the voltage at terminal 5 on the DDM side, which is 12V. This confirms that the 12V power supply is output from the DDM, and deduces that the DDM is damaged (Figure 5).
Figure 5 Damaged DDM
In addition, if the DDM continues to supply power, the driver's side window glass lifting motor will continue to operate, which will inevitably damage the motor. After disconnecting wire connector D014 and supplying power to the driver's side window glass lifter directly from terminals 20 and 10 in both forward and reverse directions, there was no response, so it was determined that the driver's side window glass lifter motor was also damaged. Remove the driver's side window glass lifter assembly (Figure 6), can smell a burnt flavor.
Figure 6 Driver's Side Window Lifter Assembly
fault resolution
Replace the DDM and the driver's side window glass lifter assembly after the test drive, the driver's side window glass lifting back to normal, troubleshooting.
Fault Summary
Measuring the waveforms of the relevant signals of the driver's side window glass lift control again (Figure 7), it can be found that the DDM controls the forward and reverse rotation of the lift motor by providing an override and power supply for the driver's side window glass lifter assembly terminals 1 and 4, thus realizing the control of the window glass rise and fall; and as long as the lift motor is running, the motor position sensor will feed back the pulse signals of 0V and 12V. As long as the lift motor is running, the motor position sensor will feed back 0V and 12V pulse signals.
Figure 7 Signal waveforms for driver's side window glass up/down control
Author：Jiande Baoyue Auto Service Center Fang Chao
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