BMW 530Li seats can not adjust from left to right(solved)

One of my auto repair technician friends sent this article material,and I write it on purpose to share this real auto repair case on solving bmw 530li seats adjust trouble.

 

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Auto information:

Mileage:47 kilometers  Engine:N52 engine   model:bmw 530li 2008

Problem:Seats can not adjust,and press ”memory button” M,can not light on.

 

Trouble diagnose:

DTCs read form ISID:

9FF0 SZM LIN communication trouble.

9FF2 SZM LIN communication trouble.

9FF1 SZM LIN communication trouble.

 

Detection plan form DTCs.

B6131_50011 Central Console Switch Center button

SZM LIN communication trouble (right keyboard)

SZM LIN communication

SZM LIN communication trouble (left keyboard )

Result remind control module communication trouble:A169 Central Console Switch Center.

 

This trouble may caused by one or more following reasons:

• Battery supplier trouble.
• Fuse trouble
• Relay trouble
• Bus line connection trouble

Technician done:

• Renewal SZM module and left-right seat switch
• Use ISID to active seats,and find the seats can adjust
• After inspecting the seats module and SZM,find the battery supplier is OK.

According to below points,we can judge that the SZM module can not receive signals from seat switch.Measure the K-bus wave shape of seats switch,it show below:

Blue wave about 2.8 v,normally 12v.

Measure resistance value between K-bus and GND,multimeter show “400Ω”.It means that there is a short-circuit on bus line. SZM,left anterior seat switch and right anterior seat switch(top configuration E60) all on this bus line.You can find the short circuit by disconnecting the corresponding line.The resistance value between seat adjust K-bus line and GND display unlimited when disconnecting right anterior seat bus line connector.This means that there is a short circuit in the right front seat. Remove the seat, find the failure, the line worn, as shown in Figure .

 

Finally,the trouble disappear after repair the worn K-bus.The wave shap also display correctly(below pic shows).