Engine & Hanbrake warning lights after repair

[TS050]

Hi,
My colleagues C4 Picasso suffered a failure of the hydraulic clutch slave unit a few days ago but before that the car was fine.
Its been in the garage and had that repaired but is now showing dashboard warning lights for the handbrake and engine.
The garage have tried clearing the faults but every time the car is restarted the faults come back.
They are saying their computer can't clear the faults and it needs fixing by an auto electrician.
I've looked at the repair process for the slave cylinder and there doesn't seem to be any electronics connected to the slave cylinder.

I've had a good search for this issue on here / google / youtube but can't find any answer.
I know the obvious thing is take it back to the garage and demand they fix it properly but just looking if this is an easy fix.
Has the garage missed something when they have repaired the car?

Thanks for any help.

[RichardW]

The handbrake fault is likely a red herring - when there is an engine fault, it puts the handbrake into manual mode. Need to know what code(s) the engine is reporting to know where to start. If it was only the slave, and it's a manual then there are no electrical connections; if it's a semi-auto then it's a completely different story!

[Sloppysod]

Just a hopeful note.
Sometimes a fault will show up while doing a repair, for example a connection has been disturbed.
However, sometimes it will dissappear again after about 5 engine restarts/short trips.
It's happened to me a few times.
Good luck.

[TS050]

Thanks for the replies.
The car is a manual.
My colleague is taking the car back to the garage tomorrow to get the fault codes.
The garage are saying the faults were already there when the car was brought in.