I once had a problem with abs light staying on. Local sparky plugged in computer and cleared code. fault caused by trailer brake light short.
Now i have imoboliser problem sometimes turn key no start, wire jump from battery to starter solenoid with ign on and away it goes, next time turn key and car starts. Purchased OBD11 unit to plug in in the hope it would give me a fault code but the OBD will not connect to ecu. YES this is a disco 1 built 98 done 160 k runs like a dream most of the time. Just for your interest i'm a pom in New Zealand