The engine control unit from BOSCH have a diagnostic connector, which depends on error code pulses .
The triple plug is near the ECU in the passenger foot-well. ( FIAT UNO )
You can use a LED. The LED has to be connected, in series with a resistor of 1k ohms, with 12V
and the white/red cable of the diagnostic connector ( triple plug ).
The LED lights when the engine control unit has something in the fault memory.
(For models from 1992 and partly from the middle of 1992, an occurring error of the control unit is shown in the dashboard by a lighting lamp)
If red an black at the diagnostic connector are bridged for 5 seconds, with the engine running, the output of the error-memory is started.

The LED flashes x * 4 by a total of a 4-digit code .
Between the flashing intervals, is a pause of 2 seconds.

0000 Start / end fault memory readout.
1111 Unknown defect of the control unit.
1232 Throttle position (engine damaged, defective Throttle)
2121 No signal from Throttle, throttle switch (short circuit, wiring, etc.)
2122 No engine speed signal (Hall sensor, ignition module, etc.). This bug is in the DIGIPLEX ignition.
2212 No signal from Throttle (short circuit, wiring, etc.)
2312 No signal coolant temperature sensor.
2322 No signal from temperature sensor in the injection system.
2341 Lambda control, limits are exceeded, the faulty oxygen sensor, secondary air, fuel injection or ignition.
2342 No signal from the lambda probe
2343 Cause see 2341
4431 Cause see 1232
4444 No error in the error memory

Deleting the error memory of the Monojetronic ECU:
Bridge black with white/red the at least 15 sec.with hot ignition.