I'm not sure if PSM is enabled by default. However, you can request your own timers using the AT+CPSMS command. See section 10.4 here: https://www.u-blox.com/sites/default/files/SARA-N2_ATCommands_%28UBX-16014887%29.pdf
To enable PSM or to modify the timers call something like:
The timer values are specified as 8 binary digits in quotes. Where the upper 3 bits are the coefficient, and the lower 5 bits are the numerator.
For the Requested_Periodic_TAU timer the coefficients are:
For the Requested_Active_Time the coefficients are:
The network has to agree to the requested timers and may not, in which case the network will provide other timers. You can query the final timers using the AT+CPSMS? command. Requesting too short (especially for the Requested_Periodic_TAU) or too long timers will likely cause the network to reject/override the requested values.
Also note, there are potentially several timer value combinations (coefficient x numerator) which results in the same amount of time. Sometimes at first glance the values seem very different to what you requested but the overall time is the same. e.g 10m x 3 or 1m x 30.