It's probably one of your LAMDA sensors has failed. You probably have 2 on your KA, one before the cat accessed from above the engine, the other after the cat accessed from underneath. You could try taking then out and cleaning them by squirting carb cleaner on them. It's not worth replacing them until you get the fault diagnosed though.
Vince
July 2013
you have an engine fault and the only way to determine your repair is to put the veh.onto a code reader
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Try fixfault.com to fix cars.