SubZero Refrigerator Freezer Error Code 90 H 80 – How to fix? by KatyApplianceRepair.com  

Sub-Zero error code EC 90 H 80 indicates
a main-board communication issue. Below is a quick reference
and troubleshooting guide for this code.

Quick Reference

Error Code	Meaning	Severity
EC 90 H 80	Communication fault between the display board and main control board	High

Cause & Solution

Cause	What to Check	Fix
Loose or corroded communication cable	Inspect cable connections between display and main board	Re-seat connections; replace the cable if damaged
Faulty main control board	Test board outputs after re-seating cables	Replace the main control board if fault persists