Siemens alarm 810003: Asynchronous error, error analysis via STEP7 required

What it means

An asynchronous error was recorded - a fault not bound to a specific program instruction, such as a power-supply glitch, slot failure or communication problem reported through the asynchronous error OBs. The HMI shows only this reduced message, so the STEP 7 diagnostic buffer is mandatory to see which OB fired and why. Recurrence patterns usually reveal whether hardware or configuration is at fault.

Likely causes

• I/O access problem to a failing or absent module
• Power-down/power-fail event on the S7 rack
• Communication/profiled interrupt errors (OB85/OB86-class events)