Land Rover Repair: check engine light, landrover discovery, engine faults

Question
my 1997 landrover discovery keeps having the
check engine light on, I took it to the mechanic and he said that it's nothing wrong with the car after testing it and reset the computer for the light to come off, but after 2 weeks the light comes on again and stays on.
I was told that if I disconect the battery for 20 minutes then start and turn off the car 3 times that the light would go off. (is this true?) I have not tried that yet.
What would you suggest.

Answer
Hello Brian,

Well you can try the 20 minute/3 restart thing if you want but I doubt it will do much.  Just disconnect the negative cable on the battery for a few seconds and that will reset the Check Engine light...until it is triggered again.

Many ECU (your vehicles computer)faults are stored in volatile memory, including engine faults.  Disconnecting the battery for a few seconds wipes the memory clean and allows the ECU to start recording the faults anew.  

It also resets all the ECU adaptions IIRC so on newer vehicles you lose the "adaptive strategies" for stuff like engine fueling and auto gearbox changes.  Whenever I have a triggered situation, I reset the warning and then look for the light to reappear.  That's when I know whether its serious or just a random error that won't be duplicated.

SO, ignore the 20 minute/3 restart suggestion:  reset the negative cable for about a minute then run your Disco as normal.  You will have to re-enter your CD Radio security code and adjust the clock.

Best of luck, Brian...

JohnMc