What method did you use to check the wiring from the ecu to the injector?
With a ohms meter I checked the resistant between the two
Normally that would be fine but this fault code is for an injector circuit malfunction.
This means the fault is either with the ecu output, the injector or the wiring.
As it only happens once it's warm would indicate either a fault with the ecu internally or a connection fault in the wiring which opens up with heat.
To test the wiring, you should isolate both ends similar to doing an ohms test but introduce a 12v supply at one end, a load at the other end and then measure the voltage drop on the wire.
Doing an ohms test wont show if a wire is broken if even one strand is touching but a voltage drop test will show that enough current wont pass through the circuit.
If the wiring proves to be good, then the fault must be in the ecu output stage.