Test Point 4 - RPM signal

TEST POINT 4 - Rpm signal - Faultcode 1_18

Possible Causes, Elimination, Remarks
Run test using an oscilloscope. Connect and adjust shop oscilloscope according to manufacturer's instructions.

Connect oscilloscope test lead with terminal 49 and terminal 48 of the disconnected DME control unit plug.




Start engine. Sinewave fluctuations of 3 V min. must now be displayed. An intermittently higher amplitude indicates the reference mark signal.

1 - Rpm signal
2 - Reference mark signal

If the voltage signal is too low (<3V), the gap between sensor and ring gear may be adjusted incorrectly.

Sensor gap: Between ring gear and sensor 1.0 +/- 0.2 mm (0.040 +/- 0.008 in). Using System Tester 9288, the reference mark signal may be read directly in the Input signals menu item.




2. Test option

Check rpm signal with test lead VW 1501.

Connect test lead between rpm sender and disconnected control unit plug. Connect oscilloscope to test lead.

On vehicles with immobilizer, pull start relay (R 61) off the central electrical system and bridge plug-in contacts 30 and 87 (identifications 3 and 5 on central electrical system) with fuse-protected shopmade cable.

Start engine

Sinewave fluctuations of 3 V min. must now be displayed. An intermittently higher amplitude indicates the reference mark signal.