Hi,
Here's the set up: Coupler 1: A16g1 and g2 (knock sensors), Coupler 2: Trimming plug. These two connectors are not relevant for your issue. Coupler 3: L5 crankshaft pos. sensor (measure about 1V AC from the pick up at crank speed!) Coupler 4 or A: pin1- signal 1 to coil, pin2-signal 31(ground), pin3- signal 15 to coil, pin 4-TN eng. speed signal to N16 MAS, pin5- shielding, pin 8- toX11/4 diagn.coupler, pin7 -to N3 inj.ctrl..
On this coupler you want to verify signal 1,15 and 31, the rest is not relevant for your "no spark" issue.
Last, coupler 5or B, you got pin1-L5/1 cam sensor, pin3- S65 AT overload protection switch, pin4-B11/2 coolant temp., pin5 shielding, pin6- 31 ground, and 7 and 8 being idle and full-load switch from throttle. Here really relevant to you are only pin 6, ground.
Let me know what you found.
All the best,
Dokta