Trane Mini Split 4-TIME BLINK Error Code

Updated 2026-08-29 · review status: manual-verified Last verified: 2026-08-29

Quick answer

4-TIME BLINK on Trane mini splits means indoor control system trouble - the indoor controller cannot read data in its nonvolatile memory, and Trane's failure-mode table directs indoor PCB replacement. Power cycle once; a recurring 4-time blink means the indoor board needs a technician.

Severity: high · DIY difficulty: beginner

Safety

Stop here: electrical or inverter work is technician-only. Do not open panels, test capacitors, touch wiring, connect gauges, add refrigerant, or keep resetting the system.

What 4-TIME BLINK means

Trane's troubleshooting table lists 4-TIME BLINK as indoor control system trouble. The service manual says the indoor controller cannot read data in nonvolatile memory and directs replacement of the indoor electronic control P.C. board in the failure-mode table.

Code meaning varies by series

  • Trane ML series (Mitsubishi-built NTXWMT/NAXWMT) service manual: Indoor electronic control P.C. board nonvolatile memory read failure - remedy per manual is PCB replacement

Causes, ranked

  1. 1. One-time control glitch that clears on power cycle occasional diy-ok

    Check: Turn the system off with the remote, then power cycle once at the breaker or disconnect if you can do that safely.

    Fix: If the code does not return, monitor; if it returns, stop resetting and schedule service.

  2. 2. Indoor PCB nonvolatile memory (EEPROM) corruption occasional pro-only

    Check: Memory faults cannot be verified without service-tool or PCB-level diagnosis.

    Fix: Technician: confirm memory fault and replace the indoor electronic control PCB.

  3. 3. Indoor PCB hardware failure occasional pro-only

    Check: Requires board-level inspection and voltage checks.

    Fix: Technician: replace the indoor PCB; do not keep resetting.

  4. 4. Wiring/connector fault on the indoor board causing false memory errors occasional pro-only

    Check: Connector inspection requires opening the unit.

    Fix: Technician: inspect connectors and retest before board replacement.

Related codes

trane/3-time-blink · trane/5-time-blink · trane/6-time-blink · trane/7-time-blink · trane/upper-lamp-0-5-second-blink

Commonly searched as: "trane 4-time blink" · "trane error code 4-time blink" · "trane air conditioner 4-time blink"

Sources

  • Trane error codes (upper lamp blink table) - SplitAtlas, sourced from Trane MyLinkDrive NTXWMT-A111A(B) Service Manual Section 9 — verified 2026-08-29
  • Mitsubishi Electric / American Standard NAXSMT-A111AA (Trane ML-series equivalent) Service Manual, 9-4 Troubleshooting Check Table — verified 2026-08-29