Test Point 23 - Speed/Reference Sensor

TEST POINT 23: - Speed/reference mark sensor

This test can only be performed with an oscilloscope. For this purpose, connect and adjust a workshop oscilloscope in accordance with the manufacturer's instructions.




- Connect the positive tester lead via a test lead to the control unit plug terminal 47 and the negative tester lead via a test lead to control unit plug 48.




- Crank the engine with the starter. Sinusoidal oscillations of at least 3 V (speed pulses) and an intermediate higher amplitude (reference mark) must be displayed on the screen.

1 - Speed signal
2 - Reference mark signal

- If the voltage signal is too small i.e. < 3V, the distance between the sensor and the gear ring may be incorrectly adjusted.

Sensor distance: Between gear ring and sensor: 1 ± 0.2 mm (0.040 ± 0.008 in).

If there is no display:

Disconnect the plug of the speed sensor at the terminal strip in the engine compartment. Connect tester leads to the middle and outer plug contacts of the plug (terminals 1 and 2, pin end) on the plug section to the sensor with test leads. Start the engine. Sinusoidal oscillations must be visible on the screen.




Speed sensor plug

NOTE:
- If terminal 3 is connected to ground, the display must remain unchanged.

- If this is not the case, check sensor for continuity, spacing and soiling.