Error E170 is an error associated with ventilation and appears when the tanning system is overheating.
On the Ergoline Essence and it's Soltron equivalent models check the following to address the issue:
Plug BU202 & ST202 check and make sure no pins have backed out. Pay particular attention to pins 7&8
Plug Bu26 & ST26 check and make sure no pins are backed out. Pay particular attention to pins 1&2, 4&5.
Plugs BU161 & ST161 and BU162 & ST 162 make sure no pins have backed out and confirm power between pins 2&5 on both plugs.
The mentioned series has temperature sensors that need to be manually reset when engaged. The decorative panels have to be removed to access these sensors. If all plugs confirm to be in proper condition, reset temperature sensors.