HEX: 99 - Glow plug / electronic ignition unit interruption

Fault Details:

Glow plug / electronic ignition unit interrupted or shorted to supply voltage UB.

Recommended Solution:

Electrical check of the glow plug. Inspect visually for damage to the unit, seal, thread, cable state, and connection pushed in and not damaged. Electrical continuity.

Note, different models and controllers might have different fault code meanings. If you're not sure, you can contact Heatso directly.