Porsche 928 Workshop Manual page 618

928 S4
928 GT
Fuel System / Electronic Control
Test point 13: Engine speed / refer-
ence mark sensor
This test can only be performed with an oscillo
scope. Connect up and adjust the workshop
oscilloscope in accordance with the manufac-
turer's instructions.
Using test leads, connect the positive tester
lead to control unit plug terminal 23, and the
negative taster lead to control unit plug termi-
nal 6.
u, T""'
35 34 33 32 31 30 2'9 28 27 26 25 24 23 22 21 20 19
":,,,
0,:
-------- ---------
1: .......
ii
I
::
- - - - - - - - - - - - - - - - - -
;: 2
18 17 16 15 14 13 12 11 10 9 6 7 6 5 4 3 2 1
:I
4
Crank the engine with the starter motor. The
screen must display sine waves of at least 3 V
(engine speed impulses), and these must in-
clude a higher amplitude peak (reference
mark).
1 - Engine speed signal
2 - Reference mark signal
If the voltage signal is too low (~3 V), dirt may
have affected the distance between the sensor
and the gear ring.
a
EZK-Diagnosis/Troubleshooting
Printed In Germany - Xxv, ,990
D28-11