04.083GPPMobile radio interface Layer 3 specificationRelease 1998TS
Cause value = 2 IMSI unknown in HLR
This cause is sent to the MS if the MS is not known (registered) in the HLR. This cause code does not affect operation of the GPRS service, although is may be used by a GMM procedure.
Cause value = 3 Illegal MS
This cause is sent to the MS when the network refuses service to the MS either because an identity of the MS is not acceptable to the network or because the MS does not pass the authentication check, i.e. the SRES received from the MS is different from that generated by the network.
Cause value = 4 IMSI unknown in VLR
This cause is sent to the MS when the given IMSI is not known at the VLR.
Cause value = 5 IMEI not accepted
This cause is sent to the MS if the network does not accept emergency call establishment using an IMEI.
Cause value = 6 Illegal ME
This cause is sent to the MS if the ME used is not acceptable to the network, e.g. blacklisted.