Suunto DX User Guide
Error state (algorithm lock)
Suunto DX has warning indicators that alert you to react to certain situations that would significantly increase the risk of DCI. If you do not respond to these warnings, Suunto DX enters an error state and shows Er on the display. This indicates that the risk of DCI has greatly increased.
If you omit decompression stops for longer than three (3) minutes, the RGBM algorithm is locked for 48 hours. When the algorithm is locked, no algorithm information is available and Er is shown instead. Locking the algorithm is a safety feature, highlighting that the algorithm information is no longer valid.
In such a condition, you should descend back below the ceiling level to continue the decompression. If you fail to do so within three (3) minutes, Suunto DX locks the algorithm calculation and displays Er instead, as shown below. Note that the ceiling value is no longer present.
In this state, you significantly increase your risk of decompression sickness (DCS). Decompression information is not available for the next 48 hours after surfacing.
It is possible to dive with the device when the algorithm is locked, but instead of the decompression information, Er is shown.
If you dive again in this error state, the algorithm lock time resets to 48 hours when you surface.