MRCOOL / DIY 5th Generation
EC 54 error code
Compressor discharge temperature sensor TP sampling voltage is lower than 0.06V or higher than 4.94V.
- Severity
- technician
- Verified
- Jul 18, 2026
What triggers it
Compressor discharge temperature sensor TP sampling voltage is lower than 0.06V or higher than 4.94V.
What to do
- Check the connection between the outdoor temperature sensor and the outdoor PCB.
- Correct the wiring if the sensor is not properly connected.
- Measure the sensor resistance value against the manual's temperature sensor table.
- Replace the sensor if the resistance value is not acceptable.
- Replace the outdoor main PCB if the sensor resistance is acceptable.
Which systems show it
- MRCOOL DIY 5th Generation single-zone 9k, 12k, 18k, 24k, and 36k D25 indoor/outdoor models listed in manual section 1.1.
- For certain models the outdoor unit uses a combination sensor where T3, T4, and TP are the same sensor.
Related codes
Technician scope
Sensors, outdoor PCB
Source
- Document
- data/sources/mrcool-diy5-service.pdf
- Section
- 4.7 TS05-ODU: Outdoor temperature sensor error diagnosis and solution
- Page
- 64