ErrorCodePro · Appliance Error CodesTrane AC & Heat Pump Error Codes: Full List & Meanings
Every Trane ac & heat pump error code we have verified against Trane's own support pages, with its official meaning. This list covers 5twr4 split system heat pumps (defrost control led). Codes vary by model, so confirm in your owner's manual. Support: Trane dealer (trane.com).
Codes by system
All Trane ac & heat pump error codes
Codes marked "Reset only" or "Service" have no separate page because the manufacturer publishes no owner fix beyond a reset or a service call.
| Code | Official meaning | System | Owner action |
|---|---|---|---|
| 9 flash | The outdoor temperature dropped below 3°F, so the heat pump locks out. It turns off at -7°F and back on at 3°F. This is a protection feature. | Status / reminder | Service |
| 1 flash | The manufacturer lists 1 flash as: ambient temperature sensor out of range. A licensed HVAC technician must diagnose this. | Sensors | Service |
| 2 flash | The manufacturer lists 2 flash as: coil temperature sensor out of range. A licensed HVAC technician must diagnose this. | Sensors | Service |
| 3 flash | The manufacturer lists 3 flash as: low pressure switch open. A licensed HVAC technician must diagnose this. | Heating | Service |
| 4 flash | The manufacturer lists 4 flash as: hard lockout (clears only with a power cycle). A licensed HVAC technician must diagnose this. | Control / electronics | Service |
| 5 flash | The manufacturer lists 5 flash as: soft lockout. A licensed HVAC technician must diagnose this. | Control / electronics | Service |
| 6 flash | The manufacturer lists 6 flash as: defrost cycles too close together. A licensed HVAC technician must diagnose this. | Heating | Service |
| 7 flash | The manufacturer lists 7 flash as: timed defrost mode (check ambient sensor placement). A licensed HVAC technician must diagnose this. | Sensors | Service |
| 8 flash | The manufacturer lists 8 flash as: timed defrost mode (check coil sensor placement). A licensed HVAC technician must diagnose this. | Sensors | Service |
Symptoms
Sources
Last reviewed: October 20, 2026. ErrorCodePro is not affiliated with Trane.