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Ignition system, glow plug system > < Checking the data BUS

Fabia Mk1

Testing cruise control system
Testing cruise control system
Apart from the control switch on the steering column switch the cruise control system (CCS) has no other components. All functions are carried out by the engine control unit - J248-. The data from the operating switch to the engine control unit - J248- are transferred over the databus by the electrical system control unit -J519-. The CCS is active above a speed of 30 km/h.
Special tools and workshop equipment required
t  Vehicle system tester -V.A.G 1552 -
t  Diagnostic cable -V.A.G 1551/3- or -V.A.G 1551/3A- or -V.A.G 1551/3B-
t  Hand multimeter (e.g. -V.A.G 1526 A-)
t  Adapter cable set (e.g. -V.A.G 1594 A-)
t  Test box -V.A.G 1598/31-
Test conditions
l  Fuse no. 28 o.k.
l  Cruise control activated.
–  Activate the cruise control → Chapter
Check for proper operation
–  Connect vehicle system tester - V.A.G 1552-. Switch ignition on and then select “address word” 01 Engine electronics → Chapter.
–  Select function 08 “read measured value block” and display group number 006.
   
–  Readout on display:
–  Observe the display in display field 4.
   Specified value:
   0 = CCS disconnected
   1 = CCS connected
–  If the display does not occur as described:
–  Select function 06 “End output” and confirm with Q.
–  Switch off ignition.
  
Reading measured value block         6   ->
0 km/h       000         0 %          0
–  Inspect the CC switch with the hand multimeter (resistance measurement) according to the following table:
  N23-0199
Switch position of the CC switch10-pin plug on CCS switch, contactSpecification
Switch B on “ON”4 + 5
6 + 7		max. 1.5 Ω
Switch B on “RES”4 + 5
2 + 7
6 + 7		max. 1.5 Ω
Switch A pressed3 + 7max. 1.5 Ω
Switch B pressed to “OFF”6 + 7
4 + 5 		max. 1.5 Ω
∞ Ω
Switch B to “OFF” locked6 + 7
2 + 7
4 + 5		∞ Ω

If the specified values are not reached:
–  Replace CCS switch.
If the specified values are reached:
–  Test the wires of the CCS switch to the vehicle voltage control unit -J519- according to the current flow diagram.
   
–  Test the wire from the CCS switch to fuse 28 for interruption or short-circuit.
–  Connect test box -V.A.G 1598/31 - to diesel direct injection system control unit - J248-. The wiring loom of the control unit is not connected → Chapter.
–  Check the following wire for interruption or short-circuit to earth or positive:
  S01-0094
10-pin plug on CCS switch, contactTest box -V.A.G 1598/31-, bush
245
344
414
546
714

–  Connect handheld multimeter for voltage measurement between contact 6 of plug and earth.
Specified value: approx. battery voltage
–  If necessary eliminate wire interruption or short-circuit.
If the lines are not found to be faulty:
–  Perform self-diagnosis of onboard supply control unit -J519- → Electrical System; Rep. Gr. 90
–  Checking the data BUS → Chapter
   

Ignition system, glow plug system > < Checking the data BUS