As the owner of a series of LR Discoverys, which have more ECUs than anything else in the universe, I feel the pain.
Garages can only do diagnostics to a certain level.
"Fault code says blah. We need to replace the XXX at a cost of £XXX".
OK.
But it doesn't fix the problem.
Back a week later with the same issue.
Replace something different.
Can you put back the expensive thing you swapped last week, and refund me?
"No."
There's no *real* fault finding.
Just guessing ( at your expense ).
That makes me appreciate the citreon garage in armley, Leeds, even more.
Garage in dirty building under a railway, no frontage, cars parked up along the road one wheel up on pavement. Interior is filthy, one ancient mechanic has until, half-smoked dog-end permanently stuck to his lip. It's ice-cold, no heating. Air reeks of oil and grease.
I took my Citreon in with an engine management light flashing.
"We've run the diagnostics and the fault codes indicate a problem with braking sensors. Tested the sensors and they are fine. Reset the ECU and cleared fault code listing - the ECU is correctly detecting the sensors. Possibly a dirty connector giving a false signal. Bring it back if the light comes on again. No, no charge."
Proper mechanics who have kept up with the times.
Probably no coincidence that half the taxi firms in Leeds seemed to have their cars in there for work.