Thanks for your question I was able to get the following information:
The most obvious thing to check is that you have nitrogen going to the instrument at the proper pressure. Then, the sensor that you just installed may need to be adjusted. Underneath the yellow sticker on the sensor there is a little screw. Try adjusting that screw either direction to see if that clears the fault. If not, you may need a new gas controller.
Are you sure you don't mean the exhaust is bad? It's been a long time since I worked on a 150 but I don't recall there being a "jumpable" sensor for the curtain gas.
[b]Thanks to R. Kuntz for providing this answer.[/b]
In my experience a bad exhaust error can be solved by adjusting the exhaust gas flow (pressure) to the system. This also happens sometimes on the API4000 systems we use.
[b]Thanks to C. Swaanen for providing this response to LabWrench. [/b]