Electronic Fault. On-Board Computer Failure.
However, there are other reasons why the injection warning light may be illuminating.
It could be from something as simple as water in the fuel filter. One of the most common faults is because of the EGR Valve (Exhaust Gas Recirculation Valve) so it may be worth checking that.
If you have the experience to do the work your self it is best to do so, however if all else fails, have the ECU (Electronic Control Unit) Checked by a compatible Diagnostic Kit.
I Think its the EGRV though, as it is a very common thing to happen on them. If you go to your garage, you can have a new one fitted for around £170, as they are not repairable.