When suspecting a faulty ECU or faulty injectors in case of a guaranteed ECU failure all 4 injector codes below need to be present:

P0201
P0202
P0203
P0204

Possibly also available during diagnosis:

P0245
P0246

Potential other codes triggered by the ECU fault
P0300
P0301
P0302
P0303
P0304

If all 4 injector codes are triggered the solution is:
Replace the ECU. Before replacing check the injector wiring harness to see if all wires are still intact.
Saab 93 T8 ECU repair service - is the solution to your problem.

In case of 1 injector failure diagnose said injector, ignition coil, spark plug and lastly wiring.