GLA-521

QA. DTC 521





Condition
Diagnostic trouble code (DTC) GLA-521 is stored if the control module registers that the central locking switch unlocking or locking signals are less than 1.5 Vfor 10 seconds when the ignition is switched on.

Substitute Value
None.

Possible Source
The central locking switch in the driver or passenger doors is sticks or has caught in the locking or unlocking position.
Short-circuit to ground in signal cables from central locking switch in the driver or passenger doors.


NOTE: A diagnostic trouble code (DTC) may be stored if the central locking switch is held in the unlocking or locking positions for at least 10 seconds. Fault causes of this type are not included in the fault tracing procedure.


Fault Symptom(s)
When the fault occurs, all doors are locked or unlocked and the central locking system stops working.

Start fault-tracing with QB.


QB1. Checking Signal From Central Locking Switch





Go into scrolling values.
Read off central locking switch status.
The value of both signals should be HIGH.
Is the value of both signals HIGH?
Yes: Go to QB8.
No: Go to QB2


QB2. Checking Central Locking Switch





Remove central locking switch from driver's door.
Disconnect central locking switch.
Go into scrolling values.
Read oft central locking switch status.
The value of both signals should be HIGH.
Is the value of both signals HIGH?
Yes: Go to QB3.
No: Go to QB4.


QB3. Replacing Component


Replace central locking switch for driver's door.
Then continue with QB8.


QB4. Checking Central Locking Switch

Remove central locking switch from passenger door.
Disconnect central locking switch.
Go into scrolling values.
Read off central locking switch status.
The value of both signals should be HIGH.
Is the value of both signals HIGH?
Yes: Go to QB5.
No: Go to QB6.


QB5. Replacing Component

Replace central locking switch for passenger door.
Then continue with QB7.


QB6. Checking Cables





Check cables between control module #A18 and driver's door central locking switch #02, between control module #4 and driver's door central locking switch #C2, between control module #A16 and driver's door central locking switch #C4, between control module #A16 and passenger door central locking switch #C3 and between control module #A4 and passenger door #C5 for a short-circuit to ground according to WWA3 WW. Checking Wiring and Connections
Then continue with QB7.


QB7. Verification






Hint: After repairs have been completed they must be verified as follows to ensure that the fault has been eliminated:

Reconnect connectors, reinstall components.
Go into scrolling values.
Read off central locking switch status.
The value of both signals should be HIGH.
Is the value of both signals HIGH?
Yes: Fault corrected
No: Fault not found


QB8. Intermittent fault





Check cable between VGLA control module terminal 17A and tilt sensor for an intermittent short-circuit to ground according to. Check cables between control module #A18 and driver's door central locking switch #C2, between control module #4 and driver's door central locking switch #C2, between control module #A16 and driver's door central locking switch #C4 between control module #A16 and passenger door central locking switch #C3 and between control module #A4 and passenger door #C5 for a intermittent short-circuit to ground according to WWB3 WW. Checking Wiring and Connections Operation done.