hi , had a problem this morning , went to start the car and got the dreaded click click , flat battery , got a jump start and the VCM display is now not showing how many kilometers fuel i have left , or litres/kilometers , ave speed , but tells me how many k’s i have travelled and how much fuel i’ve used. any help here will be much appreciated. Mark .
not sure about the 88 but on my car (94) pushing the turn signal arm in toward the steering wheel makes the display cycle through all available displays …
Larry the 87-92 (3?) use individual buttons which allow a short cut direct to which ever function you wish to display.
So does the 94, Robin …it’s just that I find it quicker to pump the turn signal stalk to loop through the displays 
Interesting, I don’t think that was an option on the ‘92 that I had.
I came upon the function one day by accident as I usually like to have the milometer display my thirsty fuel consumption. By banging the stalk, I suddenly saw the display “move on”.
Oh and BTW, after a battery disconnect the display always defaults back to the “first” option, in my case, the mileage (kilometerage?) display 
Makes the horn honk on my 89!
Push and hold m/c or vcm.
All of the above done , nothing works , have a unit from a parts cars will swap them around and see what happens . Not a must have , but nice to know (roughly) how many k’s you have left.
Don’t ya just love Jag electrics , haven’t driven her for two days , go out today and all is back to normal , all Trip computer functions work perfectly . Go figure . I’m not complaining . Mark
Might be the start of the solder joints cracking on the transformer that hangs off the circuit board underneath the VCM buttons?
Go figure, my cruise control was out for weeks, then on a lark I pushed the button and it worked!