As said.....depends, plugging it in and reading codes is a mere few moments, interogating the system settings and getting them right could take a short while depending on what they find and if the data is scrambled or not requiring a reprogramming.
Fingers deeply crossed for you.
To the Hall of Doom (mechanics) only to be told:
"We've removed steering cowl and removed plug and shorted pins 1 - 7. That allows the key to turn into position 1 that brings up the dash. But the start mode is still inhibited, engine just won't turn. Also the steering lock seems not to be releasing fully. The diagnostic is not conclusive as to where the fault lies if there's a single fault. But your key barrel, coil, and are releasing fine to ignition position now.
"The key that was working fully doesn't, the key you say wasn't fully working now does. The remote lock / unlock works.
"We suggest the XYZ switch as that could be the reason why start's not happening. If it's not that then it'll be a new steering column which is £6,000. Or a re-manufactured one, which I don't know yet the prices of.
"We would only fit an OEM new XYZ switch which is £580 inc VAT +1 hour of labour. We have only ever had two RRs with fault like this -- one was the XYZ switch, the other was the steering column lock which is integral to the whole column assembly so can't be bought and fitted seperately".
I have authorised the XYZ switch but I see that there are several used offered with warranty around. Guess the usual risks apply -- I've never got s/h electrics for any of my Jags but there again I've never had such a fault with them (three XJ8 over six years + seven years with various Citroen CX and a DS -- reported as
notoriously bad in the electrics dept.)
I have asked that they check the steering column switch (solenoid?) area to see whether there's any marks of hammering as have read that some have reported that this can free the solenoid.
Does this all make sense and fit with what the guru's in here know or have gleaned?