ESP32-CAM only 2 MB PSRAM available instead of 4 MB

[Rola16a]

I am using the ESP32-Cam (AI-Thinker) in the watermeter project (jomjol/AI-on-the-edge).
My ESP32-S should have 4 MB PSRAM. However if I use this ESP in the project I get the error message „not enough PSRAM available, expected 4.194.304 Mbyte – available 2 MB, either not initialized or too small or not present at all, firmware can not start“
I decided to buy onother ESP32-Cam from an other provider, but the error message is identical.
If I store a reference image (VGA) as required by the project the ESP32-Cam does not work properly Wifi is often disruped.
If I lower the resolution of the image to QVGA the ESP32-Cam seems to work as expected. However I still get the identical error message.
My questions are:
How can I check how many PSRAM the ESP32-Cam has?
Do I have to initialize the missing 2 MB, and how can I do it?

[ESP_Sprite]

Your bootup messages should tell you PSRAM is detected and what size it has. 2MB PSRAM chips are available and used sometimes (depends on whatever the manufacturer decides to use), so it could be your board indeed only has so much available.