Abstract: A diagnostic mechanism for processing diagnostic data transferred from a host computer (e.g., a motor vehicle computer) to a portable computer (e.g., a personal digital assistant (PDA), cellular phone, etc.) An alert is provided based on a comparison in the portable computer of a threshold variable (e.g., generated from a desired threshold value input into the portable computer by the user) and a diagnostic variable (e.g., fuel remaining, service interval, etc.) generated from the diagnostic data. Preferably, the alert includes a calendar entry displayed on a PDA. The alert may further include an alarm at a time-of-day preceding an alarm clock setting of the PDA. Consequently, the user does not have to rely on his/her memory to arise earlier in the morning to fill up with gasoline, for example. Preferably, the PDA receives the diagnostic data in response to being placed in a cradle mounted in a vehicle passenger compartment.