Faulty Engine-Speed Measuring Channel - Bosch ETT 008.31 Repair Instructions

8.10

Faulty engine-speed measuring channel

In the case of an error message concerning engine-speed measurement:
- Check that the selector button for 2-stroke / 4-stroke is correctly set.
- Check whether the fault can be remedied by installing a new clamp-on speed sensor.
- Check the pulse input.
This check can be made without opening the device.
The engine-speed input can analyze square-wave signals from U
significance, provided that the interval between the shorter edges is no less than 5 ms.
Connect the square-wave generator (5 Hz to approx. 150 Hz) to the engine-speed input as illustrated.
The signal polarity is unimportant.
Set signal amplitude to U ZV.
Set signal frequency to 5 Hz.
Start analysis on the exhaust-gas analyzer
(press "Pump" button). Test the signal frequencies
in accordance with the adjacent table.
If the result of this test is negative, the exhaust-gas
analyzer must be opened.
- On the "sensor board" module, check that the supply voltages are being fed correctly.
- Check power supply to sensor board according to Section 8.15.
If faulty, additionally check power supply to motherboard to Section 7.17. Replace defective components as appropriate.
- If the voltage supply is intact, in order to isolate the problem, check whether the input pulses on the sensor board are being processed.
To do this, connect the logic probe of the oscilloscope to the test point (INT-O) of the sensor board
(reference point MA-X83, PSVD = X 82).
- Repeat the above test of the pulse input using a clock-pulse generator.
L-pulses can be measured with a logic probe.
If measuring with an oscilloscope:
Each edge change of the input signal generates an L-pulse of 5 ms
The signal can also be measured on the motherboard at test plug X 30 b 19.
! Extra caution is necessary for this type of measurement. Do not cause a short circuit between the pins!
Depending on the results of your tests, replace the sensor board, motherboard or connecting cable.
44
> 2 V if they are sufficiently steep. The interpulse period is without
SS
G
2 V
459512/5Ha
Frequency Displayed value
(Hz) 2-stroke
5 Hz 1200 rpm
to to
39.5 Hz 9480 rpm
40 Hz - - - -
to - - - -
79 Hz - - - -
80 Hz - - - -
2
1 3
4-stroke
600 rpm
to
4740 rpm
4800 rpm
to
9480 rpm
- - - -