Vtec220

Hi - there is an HKS turbo timer fitted to my car which I am having problems with - sometimes after I turn the ignition off, the engine continues to run for 1 minute, which is the setting for the timer just now. Other times the engine turns off after only 5 seconds, as it did just now. Anyone know why it is doing this and what to do to sort it. Posted this in technical but no replies - need to know before the turbo etc gets wrecked!. Thanks for any help guys. Cheers.