Test Point 15 - Economy Control (Only FRG)
TEST POINT 15 - DME 944Economy Control (Only FRG)
The economy control comprises chiefly evaluation electronics integrated in the tachometer. The electronics calculates the instantaneous fuel consumption in ltr./100 km on the basis of engine speed, engine temperature, injection time signals and road speed.
Injection time signals are transmitted via a 4-pin plug (term. 1) behind the glove box to the evaluation electronics in the instrument cluster.
Checking:
Whether speedometer signals are available on sun roof lifting relay G 18, term. 1.
Connect oscilloscope between B + and term. 1.
Lift car, run engine at idle speed and engage 1st gear.
Rectangular signals must appear on the oscilloscope.
Repeat same test on instrument cluster plug B 15.
Connect oscilloscope on four-pin plug term. 1.
Run engine at idle speed - oscilloscope must display fuel injection signals (ti) (depending on type of scope, screen will display many AC oscillations).
Repeat same test on instrument cluster plug B 5.
Instrument cluster plug B 16 must have B +.
Instrument cluster plug A 3 must have ohmic water temperature signals.
Water temperature: ~60 °C ~140 ohm
~90 °C ~50 ohm
~100 °C ~38 ohm