Gear position switch

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A gear position switch is located on the automatic gearbox and is used to inform the BCU of the gear selector lever position. The BCU has four sensing inputs from the gear position switch contacts W, X, Y, Z, which are used to determine the gearbox drive status at any particular instance. The BCU gives an output corresponding to the gearbox status derived from the gear position switch inputs. The logic states defining the gear selector positions are listed in the table below, where Z1, Z2, Z3 and Z4 represent intermediate states which exist as the selector lever position is changed:

PIN DESCRIPTION

Gear position	Switch contacts
W	X	Y	Z
P (Park)	1	0	0	0
Z1	1	1	0	0
R (Reverse)	0	1	0	0
Z1	1	1	0	0
N (Neutral)	1	1	1	0
Z2	1	0	1	0
D (Drive)	1	0	1	1
Z3	1	1	1	1
3	0	1	1	1
Z4	0	0	1	1
2	0	0	0	1
Z4	0	0	1	1
1	0	0	1	0

The existence of an intermediate state causes a fault code to be detected by the BCU. To reduce the chances of the fault condition occurring while changing selector lever position, the inputs are de-bounced and only considered valid when they have existed for at least 33 ms.