Hello,
I suspect this is a result of outdated software; however, the "Trouble-shooting" guide (URL https://fedorahosted.org/sssd/wiki/Troubleshooting ) requested I post occurrences of "System Error 4" encountered to this list...

My IPA Server is RHEL65 running ipa-server-3.0.0-37.el6.x86_64
 in a lab environment.  Other RHEL65 clients haven't demonstrated this problem, but CentOS71 clients running ipa-client-4.1.0-18.el7.centos.3.x86_64 fail to accept password authentication and report messages similar to the following in /var/log/secure :

Aug 24 10:34:49 testhost sshd[17787]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=testhost.example.com user=testuser1 Aug 24 10:34:49 testhost sshd[17787]: pam_sss(sshd:auth): authentication success; logname= uid=0 euid=0 tty=ssh ruser= rhost=testhost.example.com user=testuser1 Aug 24 10:34:49 testhost sshd[17787]: pam_sss(sshd:account): Access denied for user testuser1: 4 (System error) Aug 24 10:34:49 testhost sshd[17787]: Failed password for testuser1 from 10.10.1.232 port 39617 ssh2 Aug 24 10:34:49 testhost sshd[17787]: fatal: Access denied for user testuser1 by PAM account configuration [preauth]

Help much appreciated in tracking down/fixing the root cause. 

Thanks in advance,

== k+ ==