They are trying to run Diagnostics on the vehicle.
Note that this vehicle was with them 2 weeks ago and they speculated and replaced 2 relays. THis was clearly not the issue. They also said that nothing was showing up in the diagnostic machine.
If the problem is intermittent then it is very hard to fix if it is working when the mechanic checks it.
Anyone would be "lost" at that point! Hard to guess at it with any success!