Bulbs

Don't you just hate it when something electrical goes wrong? One of the indicator bulbs on my car needed replacing. The car's instruction manual said that a high degree of technical skill is required to replace it - which excludes me.  I took the car to Halfords who fixed it. But then, on my drive home, a warning light told me that now a brake light was malfunctioning.  I returned to Halfords who fixed it happily and for no charge. Excellent customer service.  This picture was the view as I waited for the replacement to be completed.

It set me thinking, about the sophisticated error messages displayed by modern cars.  What happens if the error message is, itself, faulty?  Is there then no fault or many?