SIM Card problem with temperature test


I’m currently doing some temperature tests on the Q2686 module using an Dutch Vodafone SIM Card.
When using the device at room temperature everything is working fine. But, when I put the device in a temperature decreased environment and drop the temperature to -20 degrees, then I get an error: +CME ERROR: 13. Which means there is something wrong with the SIM card (interface).
I know from our customer that this SIM card also works at temperatures below -30 degrees.

I also did the following test: I soldered a 15 cm flat cable to the SIM card connector contacts to be able to put the SIM card connector with the SIM card outside of the temperature decreased environment, so it would not be cooled down. The device is functional correctly. This would mean that the SIM card isn’t working at temperatures below -20 degrees.
To be sure about this conclusion I only put the extended SIM card into the temperature decreased environment. So, I expected that the errors would come up. But, they didn’t come. Everything worked alright.

So when the complete modem is put in the temperature decreased environment the errors come. There is some form of dependency between the modem and the SIM card related to decreasing the temperature. Maybe, both the modem and the SIM start to compensate for variations of the clock.

Some ideas?