SEAT Workshop Service and Repair Manuals > Leon Mk1 > Power unit | Motronic Injection and Ignition System | Mixture preparation system, electronic inj.,Gas

Speed signal: checking

Special tools and workshop equipment required

t	Hand multimeter -V.A.G 1526 A- or multimeter -V.A.G 1715-

t	Fault reader -V.A.G 1551- or vehicle system tester -V.A.G 1552- with cable -V.A.G 1551/3B-

t	Auxiliary measuring set -V.A.G 1594 C-

t	Test box -V.A.G 1598/18-

t	Current flow diagram

Test conditions

l	Speedometer OK, checking: → Electrical system; Rep. Gr.90

Checking process

Note!

To check the speed signal, the vehicle must be driven. To do this, a second person is necessary.

–	Connect fault reader -V.A.G 1551- (-V.A.G 1552-). Start engine and enter “address code” 01 to select engine control unit. (Fault reader: Connecting and selecting the engine control unit → Chapter.)

Indicated on the display:

–	Press keys 0 and 8 for the function “Read measured value block” and confirm entry with the Q key.

Rapid data transfer                 HELP

Select function XX

Indicated on the display:

–	Press keys 0, 0 and 4 for “Display group number 4” and confirm entry with the Q key.

Read measured value block           HELP

Input display group number XXX

Indicated on the display: (1…4 = display zones)

–	Carry out a test drive, taking into account the display indication (requires assistance from a second person).

Specification: Display = approx. reading of speedometer

–	Press the → key.

–	Press keys 0 and 6 for the “End output” function and confirm input with the Q key.

If the indication does not change:

–	Switch ignition off.

Read measured value block 4           ->

         1         2         3         4

–	Connect test box -V.A.G 1598/18- to control unit wiring harness.

–	Switch the multimeter at the measurement margin for the aux. cables and connect it between test box sockets 1 and + 36.

–	Switch ignition on.

–	Lift the front left-hand wheel.

–	Rotate the front wheel and observe voltage display.

Specification: fluctuating between 0 and at least 4 volts

If the display does not fluctuate:

–	Check wiring to speedometer/speedometer sender → Current flow diagrams, Electrical fault finding and Fitting locations.

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