LiftMaster · Garage Door Opener Moderate
4-1 — Door obstruction detected
Opener sensed contact with an obstruction while closing and reversed, or hit resistance while opening and stopped. Repeat detections in one cycle latch the 4-1 alert.
- Keep using it?
- Yes, with caution
- DIY difficulty
- Easy
- Verified against
- liftmaster.com ↗
How to fix it
- Inspect the floor and track for anything in the door's path.
- In freezing weather, break the seal free with a putty knife and salt the threshold.
- Sight down the track for kinks, bends, or loose lag bolts.
- Pull the emergency release and confirm the door balances at the halfway mark.
- Lube rollers, hinges, and track joints with white lithium grease.
- If still tripping, slightly increase down-force (1/8 turn) — then re-test reversal with a 1.5-inch block.
- Replace weak spring or worn rollers if balance test fails.
Why it happens
Typical signs: Door reverses immediately or partway down · Door stops on the way up · Up arrow blinks 4, down arrow blinks 1 · Recently happened after cold snap or new weather seal
- Object in the door's path Trash can, ladder, parked car bumper triggering contact reversal.
- Bottom seal frozen to floor Ice bonding seal to concrete creates instant resistance.
- Damaged or bent track Track ding or roller hangup causing a hard spot in travel.
- Spring weakening Door is heavier than the down-force was calibrated for.
- Brand-new heavy weather seal Stiff replacement seal increases close force needed.
Parts you may need
If diagnosis points to a failed part, these are the common replacements. As an Amazon Associate we earn from qualifying purchases.
More LiftMaster garage door opener codes
Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician. Verified against manufacturer documentation: liftmaster.com.