Abstract: A method is provided for use in maintenance of a vehicle. The method includes an onboard computer including an onboard reasoner diagnosing a failure mode onboard the vehicle using an onboard diagnostic model. The onboard reasoner further determines a service recommendation of a service action to address the failure mode. The method also includes an off-board computer including an off-board copy of the onboard reasoner receiving a measure of fix effectivity of the service action as performed to address the failure mode. The off-board copy diagnoses the failure mode or an alternate failure mode, from the measure of fix effectivity of the service action, and using an off-board copy of the onboard diagnostic model. Responsive to diagnosis of the alternate failure mode, the off-board copy determines a maintenance recommendation of a maintenance action to address the alternate failure mode, and generating a maintenance message including the maintenance recommendation.