To debug this can you please download ipmitool (its a open source tool) and run it on the ESXi box and please post the output as shown below
# ./ipmitool sdr -v
Sensor ID : Memory (0x2b)
Entity ID : 7.8 (System Board)
Sensor Type (Discrete) : Memory
Sensor Reading : 0h
Event Message Control : No Events From Sensor
States Asserted : Memory
[Presence Detected]
Thanks