Jaguar xjs 2+2 1994 4.0 engine. I am trying to trouble shoot the lucas ecm dac 11502 in a continued quest to solve a crank but no spark. I have two ecm's and the results are the same. I have focused on the inputs and outputs for any pin on the ecm that deals with ignition. I have battery and ignition switch power to the ecm. When I back probe pin #13 on the yellow connector and crank I get the 0.5 volts AC from the crankshaft position sensor to the ecm"s as stated in the electric schematics. But when I back probe pin #1 on the blue connector which is the ecm sending a pulsed signal to the ignition amplifier I get 5.2 volts dc and the schematics say it should be 0.5 volts. Is the electric schematic wrong or are the ecm"s the porblem?
John

 

The only other possible problem could be that the ignition amplifier voltage is back feeding to the ecm. the amplifier gets power from the ignition switch and also the pulsed power from the ecm. I will isolate the power from the ignition switch and see what pin #1 voltage is before and during cranking. I would think there should only be voltage at pin #1 when cranking. I have replaced the amplifier twice, so I do not think the amplifier is the problem.
John