Name in the cause table
IMSI unknown in HSS
Source: 3GPP TS 24.301 V20.1.0, clause 9.9.3.9, table 9.9.3.9.1. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: 24301-k10.zip in the 3GPP archive.
3GPP Scout / Reference / EMM causes / EMM cause #2
TS 24.301EMM cause
EMM cause #2: IMSI unknown in HSS
In plain words
The network sends this cause to the UE if the UE is not registered in the HSS or has packet only subscription.
Our summary of the spec text quoted below.
What the spec says
When it is used
This EMM cause is sent to the UE if the UE is not known (registered) in the HSS or if the UE has packet only subscription. This EMM cause does not affect operation of the EPS service, although it may be used by an EMM procedure.
Source: 3GPP TS 24.301 V20.1.0, clause A.1. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: 24301-k10.zip in the 3GPP archive.
How this page was made
3GPP Scout built this page from TS 24.301 V20.1.0 as indexed on 2026-10-15. The quotes are copied from the spec, and code checks each one against the stored text and the 3GPP archive file before publishing. The plain-words line was written by an AI model (GPT-6 Sol) and checked against the quotes by a second AI model from another company (Claude Opus 5.5). The official 3GPP text governs.