Code 4-3 means the operator detected a loss of motor RPM while trying to close. Chamberlain Group lists a loose travel module or its connecting wires as possible causes and recommends dealer-level repair.
Read an UP / DOWN diagnostic code in the correct order
Which arrow flashes first, and how many times?
Security+ 2.0 openers with UP and DOWN adjustment arrows report a code as UP-arrow flashes followed by DOWN-arrow flashes, then pause and repeat. A 4-1 therefore means four UP flashes followed by one DOWN flash; the code does not mean '41 flashes'.
This exact manufacturer signal can feed the following diagnostic family. Keep the original code or LED pattern when troubleshooting.
What you are likely to notice
- The door starts closing, stops before the floor and reverses open
- A compatible diagnostic display or myQ path reports 4-3
- Cleaning or aligning the photo eyes may not change the behavior because 4-3 is a different diagnostic branch
Check these in order
1. Record exactly when the reversal occurs
Note whether the door reverses at the same point every time and whether 4-3 returns immediately. This distinguishes the documented motor-RPM fault from a vague intermittent closing complaint.
2. Check for an obvious mechanical bind
A door that physically binds can load the operator. Inspect the visible path and stop if the door is crooked, heavy or damaged.
3. Do not start by replacing safety sensors
The official 4-3 description points to loss of motor power/RPM and possible travel-module connections. Sensor alignment is not the primary published cause for this code.
4. Escalate travel-module or internal wiring work
The manufacturer describes this as best fixed by a dealer. Internal module connections are not a useful trial-and-error homeowner repair, especially if the opener housing must be opened.
Why 4-3 belongs in the motor/travel-module branch
The official description is unusually specific: the operator detected loss of motor RPM while trying to close, and Chamberlain Group lists a loose travel module or connecting wires as possible causes. That makes 4-3 materially different from a photo-eye alignment problem even though both can end with a door reversing open.
This is why symptom-only advice can be misleading. 'Door closes then reverses' has several branches; the diagnostic code gives you a higher-quality signal and should take priority over a generic checklist.
What a homeowner can safely verify
You can document the code, the physical reversal point, the opener model, recent service history and whether the door itself has an obvious bind. That information is useful without opening the operator housing or probing internal connections.
If recent service involved a travel module, logic board or internal wiring, mention that sequence when contacting a dealer. A fault that appears immediately after component work deserves a parts/connection check before unrelated sensors are replaced.
4-3 is a down-travel RPM-loss branch
Chamberlain Group defines 4-3 as loss of motor RPM during DOWN travel. The published behavior is a door that stops and reverses before touching the floor, and the listed causes include a loose travel-module assembly or loose travel-module wiring. That makes a confirmed 4-3 materially different from a photo-eye obstruction even though both can end with the door returning open.
Do not erase the code and begin with generic sensor alignment. Record the 4-UP/3-DOWN signal, the reversal height and whether the problem began after internal opener service. Chamberlain's dedicated 4-3 page says this condition is best fixed by a dealer, so homeowner troubleshooting should focus on documenting the branch and ruling out an obvious dangerous door bind rather than opening the operator and probing internal connections.
- Confirm 4-UP/3-DOWN and a reversal before floor contact.
- Keep travel-module assembly/wiring high in the branch.
- Use dealer/service support for internal module or wire-harness work.
Capture 4-UP/3-DOWN, the reversal height and any recent travel-module or internal opener service. If the door itself moves abnormally by hand, record that separately and stop. A technician can then distinguish a door-system problem from the travel-module assembly/wiring branch that Chamberlain associates with the code.
Stop DIY troubleshooting when…
- The opener housing would need to be opened
- The door is heavy or binds by hand
- You see damaged connectors, burned components or wiring
- 4-3 returns after obvious external obstruction is ruled out
Garage door springs, cables and a falling/unbalanced door can store or release dangerous force. Those are door-system problems, not just opener settings.
Common questions
Does LiftMaster 4-3 mean the safety sensors are bad?
The official 4-3 description points to loss of motor RPM and possible travel-module connections, not primarily to safety-sensor alignment.
Can I fix 4-3 by resetting travel limits?
A reset or travel procedure should only be used when the exact model documentation calls for it. Chamberlain Group describes 4-3 as best fixed by a dealer.
Why does the door reverse before reaching the floor?
For a confirmed 4-3 code, the manufacturer ties that behavior to the motor-RPM fault branch. Without a code, the same visible symptom can have other causes.
Manufacturer sources used
These links are the factual baseline for the diagnostic claims above. Model-specific manuals can supersede general guidance.