Computer program architecture for onboard vehicle diagnostic system

A computer program architecture for a motor vehicle on-board diagnostic system including a computer having read only, random access, and keep alive memory, comprising:

• a plurality of monitor modules for monitoring respective ones of a plurality of vehicle systems or components and for issuing a malfunction subroutine call upon detecting and verifying a system or component malfunction,
• an executive program module interfaced with said monitor modules and including a diagnostic scheduler module for controlling and coordinating a sequence of enablement of said monitor modules, a malfunction indicator light (MIL) controller module for issuing a store code subroutine call and illuminating a light in response to a malfunction subroutine call, a codes module responsive to said store code subroutine call for storing a fault code in said keep alive memory,
• wherein said scheduler module disables said monitor modules and enables and controls the sequence of running of a plurality of on-demand self test routines in response to a self test command, and
• wherein said self test routines include an engine running test, an engine off test, and an output test mode, said scheduler suspending execution of any monitor module test in response to said self test command and returning to the suspended test upon completion of the self test.