Goodman mini split error code U2
Power supply voltage abnormal.
- TypeProtection
- SystemPower supply
- Can I fix it?Homeowner checks, then maybe a tech
What U2 means on a Goodman
Supply or DC bus voltage went outside the safe window and the unit stopped. It retries when voltage recovers.
On this platform, U2 is a protection: the system stopped or throttled itself to prevent damage; many clear on their own once conditions return to normal.
Common causes
- Utility voltage sag or spike.
- An undersized generator or wire run.
- A loose power connection.
- A failed capacitor or PFC stage.
How to fix it yourself
Work through the checks below first; they resolve most cases. If they do not, the repair itself may need a technician.
- Reset the system: switch the breaker (or the outdoor disconnect) off, wait a full five minutes so the boards fully discharge, then switch it back on and restart from the remote.
- If you own a multimeter and are comfortable using it, measure the supply voltage at the outdoor unit's L1 and L2 terminals with the unit running. A 230 V system should read roughly 208 to 253 VAC.
- With power off, tighten every power connection from breaker to outdoor unit.
Switch off power at the breaker before opening either unit. Capacitors in the outdoor unit hold a charge for several minutes after power is cut.
When to call a technician
Normal voltage with a persistent U2 means the outdoor board.
Which Goodman units show U2
This page applies to Goodman e-Series wall-mount (FTXNG indoor / RXNG outdoor) units. Goodman's own documentation lists U2 as "Power supply voltage abnormal", the same definition used across the Daikin it is built on. If your unit shows a code with a different shape (for example a four-character code, or a plain number), it is from a different table; use the lookup with your exact code.
Where Goodman shows this code
Most Daikin wall units do not show the code on the unit; the operation lamp blinks. To read the code, point the remote at the unit, hold CANCEL (or Timer Cancel) for about 5 seconds until 00 shows, then press CANCEL repeatedly. Each press shows a code; when the unit gives a long continuous beep instead of two short beeps, the code on the remote is the stored fault. Units with a wired controller show the code directly. A and C codes are indoor-unit faults, E, F, H, J, L and P codes are outdoor-unit faults and protections, and U codes are system-level problems such as communication, power supply and refrigerant shortage.
Other Goodman codes
Same part of the system as U2:
U2 on other brands
The same characters do not always mean the same thing. Check the brand on your unit.
- Daikin U2 Power supply voltage abnormal
- Mitsubishi Electric U2 Discharge temperature abnormal (too high)
Questions people ask
Can I reset a Goodman U2 code myself?
Yes. Turn the system off at the breaker for five minutes, then restart it. If U2 comes back, the fault is real and needs the checks above.
Is it safe to keep running a Goodman showing U2?
Not repeatedly. A protection code means the unit stopped itself to prevent damage, and resetting it over and over can turn a cheap repair into a compressor failure. Reset once, check the basics, and stop if it returns.
Do I need a technician for Goodman U2?
Work through the checks below first; they resolve most cases. If they do not, the repair itself may need a technician. Normal voltage with a persistent U2 means the outdoor board.
Sources
- Goodman e-Series product documentation (FTXNG / RXNG models)
- Daikin residential (RA) service manuals (error code tables)
Updated September 2026. Codes and definitions vary by model year. If your manual disagrees with this page, your manual wins. Send a correction.