Disclosed are a method, system and computer program product for determining hardware diagnostics during initial program loading (IPL). A space is allocated for a diagnostics hardware table storing hardware identifications corresponding to hardware to be tested. A hardware monitor function detects new and/or defective hardware. Hardware can be manually selected. A runtime diagnostics detects defective hardware. The hardware identifications corresponding to the new, failing, and/or selected hardware are added to the diagnostics hardware table. The hardware identification to be tested is acquired during the building of a system Hardware Objects Model (HOM). A diagnostics flag is set within HOM according to the diagnostics hardware table. Diagnostics are performed per HOM diagnostics flag indication. The diagnostics table is cleared, and the operating system is run. At system runtime, diagnostics code monitors for runtime error. If an error is detected but cannot be isolated to defective hardware, the suspected hardware identification will be added to diagnostics hardware table so that it can be verified on the next system IPL.