SIM808 always returns the same temperature

Question

I have a SIMCom SIM808 module built up on my own breakout board. Whenever I query the temperature I get back the exact same temperature, 24.11 (deg C) despite the actual temperature in the room varying. This happens for days on end, over dozens of queries.

AT+CMTE?

+CMTE: 0,24.11

OK

I have tried this exact same AT command sequence on a Adafruit FONA with a SIM800H module and I get proper varying temperatures.

AT+CMTE?

+CMTE: 0,23.26

OK
AT+CMTE?

+CMTE: 0,23.29

OK

The User Manual is the same for the entire SIM800 series, So I haven't been able to find any specific guidance on my SIM808 vs the SIM800H

Everything else on this SIM808 module seems to be working well, just not the temperature. Has anyone else run into this? Is there some SIM808 specific setup I'm missing?

Answer 1

Simcom has discontinued the Temperature readout for cost down reasons. The diodes in the module which are required for temperature readout are no longer assembled. The feature was not useful anyway, as the module heats up especially when charging the battery, so the readout way alway way above the ambient temperature.

Answer 2

It seems the version of the SIM800 Series User Manual that I posted above from Adafruit (v1.09) is out of date. The newer version v1.10 from simcomm2m.com mysteriously has the AT+CMTE? command removed. I guess that is SIMCom's subtle way of saying this command doesn't work.