Sensor ohm BMW 540i 1998 E39 Workshop Manual

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51 2-4
I Door Windows
/ Anti-trap strip
Power window motors
The window motors are mounted on cable regulators. The
window motor control circuit consists of two wires for operat-
ing the motor in both directions.
The motors are activated by relays in the GM
Ill. The relays
provide either power or ground depending on the direction of
window travel. The GM
Ill controls the polarity based on a re-
quest to run the window from a window switch or a conve-
nience
openinglclosing signal.
Convenience openinglclosing
The GM Iii provides the convenience openlclose feature, pro-
viding control of the power windows (and sunroof) from out-
side the vehicle with the key in the driver's door lock. The FZV
(remote key) provides the same function for window opening
only.
Anti-trap protection is active during convenience closing from
the driver's door lock.
If the GM receives a request to operate convenience closing
or opening for more than
110 seconds, the function is deacti-
vated and a
fault code is stored.
Window anti-trap protection
4 A rubber pressure guard is located at the top edge of each
door frame. It consists of two contact strips that close when
subjected to pressure. When the contact strip closes (for ex-
ample, a hand is trapped between the top of the window and
the door frame), an anti-trap signal is sent to the GM
Ill. The
window immediately (within
10 milliseconds) reverses direc-
tion. This feature does not require
initialization.
The E39 pressure sensor finger guard has a resistance of 3
Kw and it is monitored for open circuits. When pressed, the
monitored resistance changes to
< 1 Kw. if anti-trap protection
becomes faulty the one touch window closing will not func-
tion.
Window anti-trap protection is
only active in the one touch
and convenience close modes of operation. If the window
switch is pulled and held, anti-trap protection will not function.
The anti-trap contact strip has a resistance of
1.2 K Ohm and
it is monitored for open circuits. Faults with the anti-trap sys-
tem will cancel the one touch feature requiring the window
switch be held to close the window.