Sounds much like my problem with the local Peugeot agent. I was getting the dreaded ‘engine fault’ warning light. The handbook gives about 20 different reasons why this light might show.
The garage put their latop to the diagnostic port and declared ‘new anti-pollution particulate filter required’.
Job done - €900. Following day - engine warning light on. Data sent to Peugeot tech HQ. ‘New turbo required - €1200.’
As the car still ran OK apart from occasional lapses into ‘limp home mode’ … Err - no thanks. €900 more or less wasted.
Then
The tow truck took the car to an indy garage already recommended to me months earlier by my neighbour. ‘No problem with the turbo. Particle filter fine. Problem with a sensor falsely reporting the fault code.’
They changed three sensors and the problem went away and stayed away, Cost 300€.
As with my own problem with a duff A/C unit in Spain, it depends on the competence and integrity of the people on the job. The Peugeot main dealer in Torigni was shown up to be incompetent and willing to fit major parts at great expense in the hope that the fault would be swallowed up in the process. The local indy garage knew their stuff and did only the necessary for a fair price.
One of my A/C units broke down. The A/C specialists recommended to me by the patron of the ‘hostal’ I used to stay at, [he maintaining about 35-40 A/C units,] said ‘The heat exchanger has failed’ We can replace it for €XXX. That includes €YYY labour. We would have to more or less rebuilt the unit. For €ZZZ labour less, we can fit a complete new unit.’
So these guys went short on labour income to give me a better final result, the modest additional bottom line being on new, and it turned out, much improved hardware.
Ask around at places that have many units to maintain - hotels principally - on who they use for A/C servicing.