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Skoda Workshop Service and Repair Manuals

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Test brake light switch F and brake pedal switch F47 > < Testing the signals of the air conditioning system and speed increase (only for 1.4 ltr. engines)

Fabia Mk1

Testing the speed signal
Testing the speed signal
The speed signal is generated by the speedometer sender -G22- and is produced in the dash panel insert.
The processed signal passes to contact 9 of the engine control unit and is used for idling speed stabilisation and for damping load change jolts during gearshifts.
Special tools and workshop equipment required
t  Vehicle system tester -V.A.G 1552 -
t  Diagnostic cable -V.A.G 1551/3, 3A, 3B oder 3C-
t  Diode test lamp (e.g. -V.A.G 1527 B-)
t  Adapter cable set (e.g. -V.A.G 1594 A-)
t  Test box -V.A.G 1598/31-
Test condition
l  Operation and indication of speedometer o.k., test → Electrical System; Rep. Gr.90
Test sequence
  Note
t  The vehicle must be driven in order to test the speed signal. The assistance of a second person is required.
t  Comply with the safety instructions for a test drive → Chapter.
–  Connect vehicle system tester -V.A.G 1552-. Start engine and select address word 01 “Engine electronics” → Chapter.
   
–  Enter function 08 “Read measured value block” and select display group number 005.
–  Determine by means of a test drive whether the driving speed is displayed in display field 3.
–  Select function 06 “End output” and switch ignition off.
If the driving speed is not displayed:
–  Connect test box -V.A.G 1598/31 - to the wiring loom on the engine control unit → Chapter.
–  Connect diode test lamp between bush 3 (positive) and bush 9 (speed signal) of the test box - V.A.G 1598/31-.
–  Raise vehicle until the front left wheel is free.
–  Switch on ignition.
–  Turn the left front wheel.
The diode test lamp must flash (very short signal).
If the diode test lamp does not flash:
–  Check the wiring for interruption or short-circuit to earth or positive → Current flow diagrams and Fitting locations.
  
Reading measured value block         5   ->
1380 rpm      20 %      15 km/h     Enrichment

Test brake light switch F and brake pedal switch F47 > < Testing the signals of the air conditioning system and speed increase (only for 1.4 ltr. engines)