Was gonna say cleaning the 7th injector is not needed, but already done. Doing a regen is typically not enough unless you have the PTT and watch the diff pressure sensor and its charting. The error code is pointing to the SCR unit as fault. If you have the PTT, you do a DPF regen first and look at diff pressure and test the sensors, if all looks good, do the SCR regen and test its sensors. After that if the SCR is really bad, it will show up. SCR replacement is very expensive !! Make sure its tested correctly.