Thank you for your question, my name is Steve and I am a fully qualified vehicle technician with over thirty years in the trade. Hopefully I can help.
It is difficult without the fault code which the garage have to fully diagnose the problem, they have presumably previously replaced an injector which did for one month cure the problem. You now have another problem which is assumed to be the same fault, but it is important to get the fault codes read as many different problems that can occur will give very different symptoms.
It may well be the case that the first injector has failed and no another has failed, this is not unusual and may have been the result of a poor quality fuel at some point.
You have not mentioned which size engine you have in your Peugeot but there is a fault on the diesel models which causes Internal failure of the multifunction control module (incorporated in engine bay fuse box/relay plate 1).
The Remedy for this is to first check fuse F1 in engine bay fuse box/relay plate 1 and to replace if necessary.
If the fuse has not blown or is not missing then the fault may be in the engine bay fuse box/relay plate 1. and this should be replaced.
The fault codes found in this condition are:P0001, P1417, U1108, U1308.
I hope this answers your question but do please feel free to ask me any further details by replying to this thread.
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