Checking signal from central lock
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Checking signal from central lock
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Fuse 20 for central lock blows Alarm cannot be activated/deactivated
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1.
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Check that fuse 20 is intact and supplied with current.
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2.
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Connect ISAT and select "READ VALUES" on the menu, then select "UNLOCK SIGNAL" or "LOCK SIGNAL".
Turn the key in the driver door to the right and left and read off the ISAT display.
Under activation -
"ON"
At end and neutral position -
"OFF"
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3.
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If not, connect BOB and check the voltage by measuring between:
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control module connection pin 20 and a good grounding point when locking.
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control module connection pin 11 and a good grounding point when unlocking. The voltage must be approximately 12 V for approximately 750 ms.
If the voltage is correct, proceed to step 6.
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4.
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If the voltage is incorrect, check the voltage at the central lock control module by measuring between:
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control module connection pin 12 and a good grounding point when locking.
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control module connection 8 and a good grounding point when unlocking.
The voltage must be approximately 12 V for approximately 750 ms.
If the voltage is incorrect, continue fault diagnosis according to Service Manual 3:2 Electrical system, Wiring diagram for "Central locking".
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5.
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If there is voltage, check the wiring harness for short-circuit by measuring the resistance which should be < 1 Ohm.
Measure across:
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central lock connection pin 8 and theft alarm connection pin 11.
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central lock connection pin 12 and microswitch in the driver door, connection pin 1.
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microswitch in the driver door, connection pin 2 and theft alarm connection pin 20.
If the resistance is correct in the last two steps, the malfunction is likely in the microswitch, change the switch.
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