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NTI Error Code 03 07: PCB internal error (Boiler)

Updated · by Aurora Star Tech Inc.

NTI error code 03 07 on a boiler means: PCB internal error. It is also called NTI diagnostic code 03 07.

High severityBoilerTRX

Homeowner? What NTI code 03 07 means for you

Call a technician Your boiler is reporting: PCB internal error. The boiler has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.

Safe things you can check yourself

  • Check the thermostat: right mode (Heat or Cool), set a few degrees past room temperature, and fresh batteries if it uses them.
  • Make sure the unit has power: its on/off switch (often looks like a light switch near the unit) is ON and the breaker in the electrical panel is not tripped.
  • Look at the pressure gauge on the boiler. If it reads much lower than usual or near zero, or water is leaking, call a technician.
  • Outside, make sure the intake and exhaust pipes or vent cap are not blocked by snow, ice, leaves or a nest.
  • Check that the boiler gas valve is open (handle in line with the pipe).
  • Try one reset: turn the power off for 30 seconds, then back on. If the code comes back, stop resetting and call a technician.

Call (647) 657-2977Book a service call

Licensed technicians serving Vaughan, Toronto and the GTA.

What does NTI error code 03 07 mean?

Internal fault on the main PCB.

Applies to: TRX150

Common causes of NTI code 03 07

  • Internal PCB fault
Safety: Gas, electrical and refrigerant work must be done by a licensed technician. Turn off power and gas before servicing, never bypass a safety control, and always follow the manufacturer's manual for your exact model.

NTI models that use code 03 07

TRX085TRX110CTRX150TRX199TRX199C

Other NTI Boiler codes

CodeMeaning
03 01Display EEPROM error
03 02Communication error GP-GIU
03 03PCB internal error
03 04Too many resets in 15 minutes (more than 5)
03 05PCB internal error
03 06PCB internal error
03 09Gas relay check failed
3 P9Scheduled maintenance: call for service
4 11Room sensor open or short circuit, Zone 1
4 12Room sensor open or short circuit, Zone 2
4 13Room sensor open or short circuit, Zone 3
4 30Detected accessory wired to BUS connection

All NTI Boiler error codes →

NTI code 03 07: homeowner questions

What does NTI code 03 07 mean?

PCB internal error. Internal fault on the main PCB.

Is it safe to keep using my boiler with code 03 07?

It depends on the cause. The boiler has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.

Can I reset NTI code 03 07 myself?

You can try one reset (power off for 30 seconds, then on). If NTI code 03 07 comes back, the cause is still there and a licensed technician should check it.

Who can fix NTI code 03 07 near me?

Aurora Star Tech Inc. repairs NTI boilers in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.

Homeowner help: Boiler Not Heating: What to Check

Troubleshooting guides

Source: NTI TRX150 manual, p. 91. Written in our own words as a summary; always check the original manual.

General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.

© 2026 Aurora Star Tech Inc. All rights reserved. This page may not be copied, republished or used to train other systems without written permission.

Emergency Boiler Repair

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