M800 on Hydrogen Combustion Engine

[staun]

We are working on hydrogen combustion engine, which is working with a Motec M800 engine management system.
First we installed a Bosch LSU 4.0 lambda sensor, but we could only reach a value around 1,75. We thought to solve our problem by replacing it by a Bosch LSU 4.9 sensor. We need lambda-values until around 3.
With the new Bosch LSU 4.9 we have the same problem. When the engine turns richer than 1,75, the sensor works well.
Is it possible we need to adjust something in the Motec ECU Manager (we now have version 3.5.0.16) or do we need an update so we are able to a measure leaner mixtures?
We are also trying to work with a closed loop, using the lambda value? Is it possible to give some more information about working and installing the closed loop set-up?