UniMac Washer-Extractor Error Code E Co: SCI Communications Error

What does UniMac error code E Co mean?

The front-end control on a UniMac QN washer-extractor such as the UCA020QN does not switch valves or the door lock itself. It sends instructions over a serial link, called the SCI link, to the input and output board, which does the switching. E Co appears when that link stops working. The two boards cannot exchange messages, so the control has no way to command the cycle.

The control keeps listening for replies on the link. When none come back in the expected way, it gives up and shows the code. Because nothing can be commanded, the machine stays down. The display holds E Co until power is cycled, which is the maker's operator step.

This code resembles other board link messages but it names the SCI link specifically, which narrows the search to the cable, its connectors and the board at the far end. It does not point at the water system, the drive or the motor. A single occurrence after a power surge may never return, but a repeat means the link itself needs testing.

Affected models and control systems

E Co is listed for the CHM1792C family, QN washer-extractors from 20 to 100 lb, with the front-end control and the I/O board. The example in the manual is the UCA020QN.

Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.

What you may notice

• The display shows E Co and no cycle will start
• Keys on the panel respond but the machine does nothing
• The code returns right after power-up
• Water valves and door lock stay silent

Possible causes

Listed in UniMac's documentation

• A loose or damaged SCI cable between the control and the I/O board
• A connector not fully seated at the SCI link
• A failed I/O board that does not answer the link
• Electrical noise on the SCI cable

Other likely causes — what usually sits behind error code E Co on this control. A technician confirms which one it is before any part is replaced.

• Cable routed beside a motor lead or drive harness that injects electrical noise
• Connector pins corroded by laundry-room humidity and chemical vapor
• I/O board that is powered but has locked up and stopped replying
• Cable pinched when the cabinet panel was refitted after earlier service

Safe checks before calling for service

How a technician diagnoses error code E Co

1. Read the code and clear it with a power cycle to see how fast it returns.
2. Lock out the machine and inspect the SCI cable end to end for pinches and cuts.
3. Reseat both connectors and check pins for corrosion or bent contacts.
4. Confirm the I/O board has its supply voltage and its status light is normal.
5. Swap in a known-good cable if one is available and watch the link.
6. Replace the I/O board only after cable, connectors and supply test good.

Technical reference

Document

Washer-Extractor Programming CHM1792C_SVG, Part No. F8641001ENR4, Error Codes Table 29 (pp. 100-107)

Maker documentation

UniMac owner support

Edition

Part No. F8641001ENR4, January 2020

Models / control

CHM1792C family washer-extractor (QN models, 20-100 lb) front-end control

Section

Error Codes, Table 29, pp. 100-108 (PDF pages equal printed pages)

Checked

October 2026

We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.