Mou,
As this module is not a freescale module i do not have either the module or schematic available.
I can only give you recommendations to how to find the "sinner".
typically there power is supplied to different sections of the module. e.g the CPU, RF part, e.g the PA and LNA.
you need to find out which device is "active" during sleep. One example could be that it might not be possible to actually turn off the power for the PA or LNA, or that you do not set the correct port pin for turning in off.
Br,
Mads