True Refrigerator Error Code E01 / E02 / E03 / E04: Sensor Failure
On a True cabinet with a Danfoss ERC control, E01 to E04 mean sensor S1, S2, S3 or S4 has failed to report. Write down which code shows, set a thermometer on the middle shelf, and call us with the code number.
Medium: cooling may continue in fallback mode, but control of temperature and defrost is reduced.
- Code
- E01 / E02 / E03 / E04
- Maker
- True
- Equipment
- Reach-in refrigerators
- Applies to
- Danfoss ERC
What does True error code E01 / E02 / E03 / E04 mean?
On a Danfoss ERC control, E01, E02, E03 and E04 stand for sensors S1, S2, S3 and S4. Each sensor has its own job, such as air temperature, coil temperature or display. The control reads them all the time, and when one stops returning a valid value it shows the matching code. The control may keep cooling in a fallback mode, but it cannot manage defrost or temperature as designed, so the box may warm slowly or ice up over time. The number tells a technician which sensor to start with, which saves time on the call. The code does not say which part has failed, the sensor, its wiring or the input on the board, so the next step is a measurement, not a replacement guess.
Affected models and control systems
True cabinets with a Danfoss ERC control. E01 to E04 correspond to sensors S1 to S4.
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
- E01, E02, E03 or E04 on the display
- Cabinet temperature drifting from normal
- Ice forming on the back wall over several days
- The cabinet running continuously or cycling off early
Possible causes
Listed in True's documentation
- An unplugged or loose connector on the sensor named by the Danfoss code
- A broken wire between that ERC sensor and the control
- A burned out sensor input on the Danfoss ERC board
- Ice or water that has damaged the sensor lead insulation
Other likely causes — what usually sits behind error code E01 / E02 / E03 / E04 on this control. A technician confirms which one it is before any part is replaced.
- A sensor lead stretched when a shelf or rack was moved
- A connector corroded by repeated washdowns
- A sensor displaced from its clip so it reads but not the right place
Safe checks before calling for service
- Write down which of the four codes shows.
- Set a thermometer on the middle shelf to see how the food is doing.
- Close the door and keep it shut as much as possible.
- Call us to schedule service and tell us the code number.
- Add whether the box feels warmer or colder than usual.
How a technician diagnoses error code E01 / E02 / E03 / E04
- Match the code to sensor S1, S2, S3 or S4 on the ERC wiring.
- Inspect the sensor, plug and lead for damage and moisture.
- Measure the sensor resistance and compare it with its expected value.
- Check the wire from sensor to the control for an open or short.
- Watch the sensor reading at the control after reseating the plug.
- Replace the sensor or control only after the test.
- Sensor testing involves opening the control area near live circuits.
- The fallback mode hides how much temperature control is really lost.
- A burned input on the control needs a board replacement and the right parameter data.
Technical reference
- Document
- Commercial Refrigeration General Control Guide TEC_TM_001 Rev C, Danfoss ERC p.88 Display Code Definitions
- Edition
- TEC_TM_001 | REV. C | EN, 09/3/2025, P#811072
- Models / control
- Danfoss ERC
- Section
- Electronic Control (with Display) - Display Code Definitions: Carel p. 74, Danfoss ERC/ETC p. 87, Dixell p. 96, LAE p. 110
- 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 True reach-in refrigerator error codes
Which sensor does E02 mean?
Sensor S2. The number in the code matches the sensor number.
Will the cabinet keep cooling?
It may, in a fallback mode, but with less accurate temperature and defrost control.
Can I reset it?
Not from the front. The code stays until the sensor reads properly again.
Need help with True error code E01 / E02 / E03 / E04?
A technician confirms the cause on site and gives you the price in writing before any work starts.