Do you mean limp mode, below but not above 80km/h?
The engine is put in this to prevent damage to the ignition electronics and fuel system. It does this for a reason, not for kicks.
A scanner will pick up/record a fault state — the engine/ECM cannot escape prying eyes, unless there has been some sort of modification that throws communication all akimbo.
This scanner thing can be quite the revelation; besides a fault causing the limp mode malaise, what else/how many other faults may exist, and in which computer, or all? Only a scanner, correctly operated can do this, and it will tell you if the fault is past or present (different scanners have their own nomenclature when reporting, but generally "past event" means a one-off or self-corrected error, while "present" means something happening intermittently or continuously, now). I find it very difficult to accept that a qualified techie could not report anything from a plug-in session (however, dirt in the fuel system, causing coughing and stuttering, will not log a fault; nor will a few common problems with the O2 sensor, or an incompletely disengaged immobiliser that will trip an Immobiliser Fuel Disable Signal Received fault, effectively forcing the engine into limp mode by restricting the fuel rate, pending full release of the immobiliser). Clearing a recorded fault, but then seeing it reappear again indicates something more persistent, so they'd need to take the car into the workshop and plug in to a full analyser; it costs money, yes, but it is more comprehensive than the simple under-dash scanner.
