True Refrigerator Error Code P3: Dixell Auxiliary Probe Failure
P3 on a True cabinet with a Dixell controller points to the auxiliary probe, a third sensor some models use for an extra reading. The cabinet normally keeps holding temperature. Confirm that with a thermometer, and book a visit so a second problem cannot hide behind it.
Low: the cabinet usually keeps cooling from its main probe.
- Code
- P3
- Maker
- True
- Equipment
- Reach-in refrigerators
- Applies to
- Dixell controller
What does True error code P3 mean?
P3 is the control's message that the auxiliary probe is not reporting. The T-49-HC is one model that can show it. Because the auxiliary probe is not the main thermostat sensor, the cabinet normally keeps holding temperature, and the control continues to cycle from its main probe. What you notice is the code on the display, and sometimes an alarm, while cooling continues as before. That makes P3 easy to dismiss, but the alarm can also mask a problem with the main sensor, because both would put a code on the same display. A technician checks the auxiliary probe and its plug at the control, then the probe wire for damage, and then the auxiliary probe input on the board. One common cause is simply a probe that was left unplugged after earlier service.
Affected models and control systems
True cabinets with a Dixell controller that use an auxiliary probe, such as the T-49-HC.
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
- P3 on the display
- An alarm tone
- Cabinet still holding temperature
- A pan leaning on a wire inside the cabinet
Possible causes
Listed in True's documentation
- The auxiliary probe and its plug at the control
- Damaged or pinched probe wire
- The auxiliary probe input on the control board
- A probe left unplugged after earlier service
Other likely causes — what usually sits behind error code P3 on this control. A technician confirms which one it is before any part is replaced.
- A probe wire crushed under a shelf clip
- A connector loosened when the control cover was removed
- Moisture in the plug from washdown
Safe checks before calling for service
- Confirm the cabinet is cooling by checking product temperature with a thermometer.
- Press any button if the display is alarming.
- Look inside for a pan or box leaning on the probe wire.
- If P3 stays on, book a visit so a second problem cannot hide behind it.
- Tell us whether the alarm sounds or only the display shows P3.
How a technician diagnoses error code P3
- Read the code and confirm cabinet temperature.
- Locate the auxiliary probe and inspect its lead.
- Check the plug at the control.
- Measure the probe resistance against its expected value.
- Test the auxiliary input at the board.
- Replace the probe, then the board only if the input fails.
- The probe plugs into a control board beside powered wiring.
- Telling a bad probe from a bad input needs a meter and a reference.
- A code from a minor sensor can mask a problem with the main probe, which a technician rules out.
How error code P3 differs from similar codes
P1 and P2 are the main thermostat and evaporator probes on the same control; P3 is the extra one.
Technical reference
- Document
- Commercial Refrigeration General Control Guide TEC_TM_001 Rev C, Dixell p.96 Display Code Definitions
- Edition
- TEC_TM_001 | REV. C | EN, 09/3/2025, P#811072
- Models / control
- Dixell controller
- 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
Is P3 serious?
Usually not, since the main probe keeps controlling temperature, but it should be checked.
Why does the alarm sound?
The control reports any probe it cannot read, even a secondary one.
Can it hide another problem?
Yes. That is why we suggest a visit even though the cabinet is cooling.
Need help with True error code P3?
A technician confirms the cause on site and gives you the price in writing before any work starts.