my E 320 have a misfire code p300 and p305 andp306 on 1997 Mercedes-Benz E320

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so i unplug the injector # 1 pluge in the noide light and
start the engine the light did not come on but when i try # 2 the same way i did # 1 the light flash on then off the shop technician say i could be the cumputer is bad does any
no the answer to this it been a pain i also had mercedes scan tool and it do not know what cause misfire 5 and 6 ?
(2) Answers
(1) Comments
if ignition lines are good and the spark plugs are good, check fuse panel. computers don't make mistakes. people do. may need to be reprogrammed if any serious modifications have been made to intake or exhaust.
I have check fuse near computerfive fuse plus a large fuse all good i just want to know mercedes scan tool can or should detect a bad computer because the technician say the computer is good but when i disconnect the fuel
injector connector and plug in the noide light in # 1 it did not light up when i start the car is tell you that
the computer is bad i do know tell me.? no modifications have made to intake or exhaust.