Test Point 4 - Reference Mark Transmitter
TEST POINT 4 - DME 944Reference Mark Sensor
Adjust oscilloscope as in test point 3. Connect oscilloscope tester leads on terminals 25 and 26 of control unit plug with help of test leads.
Start Engine:
A single sine oscillation should appear on the screen.
It is important that the oscillation begins with a positive flank and the screen scale shows > 2 V with a starter speed of at least 200 rpm (amount of signal amplitude depends on the starter speed).
If the voltage signal is too small (<2 V), the distance between the sensor and reference mark is excessive.
Specification: 0.8 ± 0.03 mm.
No Display:
Disconnect reference mark sensor plug on plug plate in engine compartment. Connect oscilloscope tester leads on sensor plug section with help of test leads.
Connect test leads on center and outer pins (term. 1 and 2) of plug.
Start engine.
No Display:
Check tester connections on plug.
Check sensor for breaks, spacing and dirt, replacing sensor if necessary.
Sensor adjustment: see Engine Speed Sensor. Adjustments