UniMac Washer Error Code E PS: Pressure Sensor
E PS on a UniMac QN washer-extractor means the control had no valid water level sensor reading for 30 seconds, so it stopped the cycle. Power the machine down and up, and make sure the hot and cold supply is on. If E PS returns, do not open the cabinet; a technician should check the sensor, its tube and its connector.
Medium: the cycle stops until the level signal returns, and an unknown water level needs attention.
What does UniMac error code E PS mean?
E PS is the pressure sensor error on UniMac QN washer-extractors such as the UCA020QN. The pressure sensor reports water depth in the tub to the control. The control relies on that reading to know when to stop filling and when the tub has emptied, so both the fill and the drain are judged from it. If the control gets no valid level input for 30 seconds, it can no longer judge either step safely. Rather than guess, it stops the cycle and displays E PS. The manual names three possible causes: water or a kink in the sensor tube that blocks the level signal, a loose or damaged sensor connector or wire, and a sensor that no longer sends a valid reading. The code describes the signal, not the water. The tub itself may be empty or holding water, which is why a technician looks at the level and the sensor together before deciding what to replace.
Affected models and control systems
Listed for the CHM1792C family of UniMac QN washer-extractors (20-100 lb), with the UCA020QN as the example model. It applies to the front-end control on those machines.
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
- Cycle stops with E PS on the display
- The washer does not fill, or fills and then halts
- Water remains in the tub after the cycle stopped
- The control does not move on to the next step
Possible causes
Listed in UniMac's documentation
- Water or a kink in the pressure sensor tube, blocking the level signal
- Loose or damaged pressure sensor connector or wire
- Pressure sensor that no longer sends a valid level reading
Other likely causes — what usually sits behind error code E PS on this control. A technician confirms which one it is before any part is replaced.
- Detergent foam or lint drawn up the sensor tube, leaving a plug in the line
- A hose clamp or the tube itself worked loose from the tub fitting by vibration
- Moisture in the sensor connector in a humid laundry room
Safe checks before calling for service
- Power the machine down and up again.
- Check that the hot and cold water supply is on.
- Do not open the cabinet to touch the sensor tube.
- If E PS returns, call us.
- Note whether the display shows any water level and whether water is in the tub.
How a technician diagnoses error code E PS
- Read the code, then watch a fill and drain to see whether the display reports any level.
- Verify the supply and that the tub is draining so a real level change occurs.
- Check the sensor tube from the tub fitting to the sensor for water, kinks, lint and loose ends.
- Inspect the sensor connector and wire, and measure the sensor signal against the manual's specification.
- Replace the tube, connector or sensor only after those tests, then run a complete fill and drain.
- The sensor and its connector are inside the cabinet near line-voltage wiring, so access is a technician job.
- A blocked tube, a loose plug and a failed sensor produce the same missing signal, which takes testing to separate.
- If the tub holds water while the level is unknown, the machine needs to be drained and checked under controlled conditions.
How error code E PS differs from similar codes
E PS (QN) is a missing level signal for 30 seconds. E Pr (UC Design 1) is a low level pressure switch result seen in the test cycle, so the two are not interchangeable.
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.
Related UniMac washer error codes
What does the pressure sensor do?
It reads the depth of water in the tub from the air pressure in a thin tube. Both the fill and the drain are timed from that reading.
Can E PS cause an overflow?
It can if the machine cannot sense the level. Switch the machine off, close the supply valves and call us if you see water rising.
Is it a big repair?
Often the cure is a small part or a replacement tube. We tell you the price before any work begins.
Need help with UniMac error code E PS?
A technician confirms the cause on site and gives you the price in writing before any work starts.