SplitAtlas

Error-code hub

Trane error codes

Trane's ML Series ductless systems are Mitsubishi-built, so the 9 codes below follow Mitsubishi's diagnostic conventions - including LED flash patterns on the indoor unit rather than a continuously-displayed code. Because our Trane ductless coverage is small, the Mitsubishi Electric pages cover a much larger set from the same platform and will often apply.

See Tranemini-splits ->Common FirstStatus DisplaysError Codes
Status displays
1
Error codes
9

Unit applicability

Match your unit before reading the table

This table is sourced for ML Series R-410A. If your unit is a different generation or product line not named here, the same display code may vary by generation.

ML Series R-410A2 models

Common codes first

Most broadly applicable documented codes

Ranking basis: we do not have failure-frequency telemetry. These are ordered by breadth of affected systems in the SplitAtlas catalog - the documented product line's published model count, whether the same code appears on more than one product line, and any manual applicability notes we hold. This is a breadth ranking, not a popularity claim.

UPPER LAMP 0.5-SECOND BLINK

Trane's troubleshooting table says this blinking pattern occurs when the indoor and outdoor units do not operate because the serial signal from the outdoor unit is not received for the required period. The manual directs the technician to check miswiring and serial signal.

AdvisoryTechnician
Breadth evidence
2 published catalog models on its documented product line.
Safe first check
Turn the system off and power cycle once at the breaker if you can do that safely. Do not open wiring covers or move any indoor/outdoor wires.
View the fix
UPPER LAMP 2-TIME BLINK

Trane's troubleshooting table lists this pattern for indoor coil thermistor or room temperature thermistor trouble. The failure-mode table says the control detects a short or open circuit in those indoor thermistor signals.

AdvisoryTechnician
Breadth evidence
2 published catalog models on its documented product line.
Safe first check
Make sure the indoor unit has open air around it, then power cycle once if you can do that safely. Do not open the indoor cabinet or handle sensor wiring.
View the fix
UPPER LAMP 3-TIME BLINK

Trane's troubleshooting table lists this pattern as indoor fan motor trouble. The service manual says the fan rotation feedback is not emitted during indoor fan operation.

AdvisoryTechnician
Breadth evidence
2 published catalog models on its documented product line.
Safe first check
Turn the unit off if the indoor fan is not moving or is noisy. You can check from outside that nothing is blocking the air inlet or outlet, but do not put anything into the unit.
View the fix
UPPER LAMP 4-TIME BLINK

Trane's troubleshooting table lists this pattern as indoor control system trouble. The service manual says the indoor controller cannot read data in nonvolatile memory and directs PCB replacement in the failure-mode table.

AdvisoryTechnician
Breadth evidence
2 published catalog models on its documented product line.
Safe first check
Power cycle the system once at the breaker if you can do that safely. Do not open the indoor cabinet or touch the control board.
View the fix
UPPER LAMP 5-TIME BLINK

Trane's troubleshooting table lists this pattern as outdoor power system abnormality. The manual says the compressor stops for overcurrent protection or startup-failure protection within one minute after startup, and the condition has occurred three consecutive times.

Stop useTechnician
Breadth evidence
2 published catalog models on its documented product line.
Safe first check
Turn the system off. Do not keep resetting it, and do not open the outdoor unit.
View the fix
UPPER LAMP 6-TIME BLINK

Trane's troubleshooting table lists this pattern as outdoor thermistor trouble. The service manual says outdoor thermistors are detected as shorted or open during compressor operation.

AdvisoryTechnician
Breadth evidence
2 published catalog models on its documented product line.
Safe first check
Power cycle once only if you can do that safely. Keep the outdoor unit clear of leaves or debris around the cabinet, but do not open it.
View the fix

Safe first checks

Checks you can do without opening the unit

These codes have homeowner-safe steps such as filters, airflow, condensate/drain checks, remote/controller items, or a single safe power reset. If the code returns, stop at the boundary in the card.

Trane mini-splits

Use the Trane catalog to connect these manual error codes to current model pages and replacement options.

See Tranemini-splits ->

Status displays

UPPER LAMP NOT LIT

In Trane's indoor-unit failure-mode recall table, a not-lit operation indicator is listed as Normal. It means the recall check is not showing an active stored indoor failure pattern.

Not an error
Sourced Jul 2026
Applies to
ML Series R-410A
Homeowner fix
No repair is needed for this recall-display result. If the system is still not heating or cooling, use the normal symptom checks in the owner's materials and schedule service if comfort does not recover.
Status note
This is a normal recall-display result, not a fault.
View the fix ->

All error codes

UPPER LAMP LIGHTS UP

Trane's troubleshooting table lists upper lamp lights up with the outdoor unit not operating as outdoor control system trouble. The manual says the inverter PCB or outdoor PCB cannot read data in nonvolatile memory and directs the technician to check the outdoor board LED pattern.

AdvisoryTechnician
Sourced Jul 2026
Applies to
ML Series R-410A
Homeowner fix
Power cycle the system once if you can do that safely. Confirm the outdoor unit has not been switched off at a service disconnect, but do not open the cabinet.
When to call a pro
Call a licensed HVAC technician if the outdoor unit remains off. Tell them Trane maps this steady-lamp condition to outdoor control-system diagnostics.
View the fix ->