How to Fix iTunes Error 4037 When Updating or Restoring iPhone

By ErrorFix · Updated October 23, 2026 · 6 min read

What error 4037 means

Error 4037 shows up in iTunes on Windows or Finder on a Mac while you are updating or restoring an iPhone. Apple's own table of iPhone update and restore error codes lists 4037 with a single explanation: the iPhone is locked, and you should unlock the iPhone and try again. The message typically appears when the process reaches a stage where the computer needs the phone to cooperate — verifying the install, transferring data, or switching boot modes — and the phone is sitting behind its lock screen.

The lock screen is a security barrier by design: a locked iPhone will not respond to the computer's restore commands, so iTunes or Finder aborts and hands you error 4037. This is not a hardware fault and not a firmware-signing failure — it is a guardrail doing its job. People usually hit it in one of three ways: they plugged in the phone and clicked Update or Restore without unlocking it first; the phone re-locked itself mid-process because auto-lock kicked in during a long firmware download; or the phone finished a restore into the setup screen and is still asking for a passcode while the computer tries to continue. All three are fixable without touching your data.

One important nuance: if you do not know the passcode — because the phone is secondhand, or you simply forgot it — you cannot fix error 4037 by unlocking, and no amount of retrying will help. That situation has its own official exit: the recovery-mode restore in step four, which erases the phone and the forgotten passcode together. If you do know the passcode, work through the steps in order — unlock first, auto-lock second, software third.

Common causes

• iPhone locked with a passcode when the update or restore started: the phone was never unlocked before clicking Update or Restore.
• Auto-lock re-engaged during a long download: the phone locks itself mid-process while iTunes is still working.
• Phone restarted into the setup or passcode screen mid-process: the computer continues while the phone is asking for a passcode.
• Outdated iTunes, Apple Devices, or macOS: old restore software mishandling the unlock handshake with the phone.
• Loose cable or USB dropout: the connection drops and the computer loses the unlocked state.

How to fix error 4037 — step by step

Follow these in order. The first three steps solve nearly every case — the rest cover the stubborn ones.

1. Unlock the iPhone and keep it unlocked. Unlock the iPhone and keep it unlocked. Unplug the cable, wake the phone, and enter the passcode on the lock screen until you reach the home screen. A phone that is asking for a passcode on the setup screen must be cleared there too — if you know the passcode, enter it now. Do not proceed while any lock screen is showing: the restore cannot begin until the home screen is visible and the phone responds to touch. Reconnect the phone and retry the update or restore immediately, while it is still unlocked.
2. Turn off auto-lock for the duration. Turn off auto-lock for the duration. A firmware download can take twenty minutes or more, and if auto-lock is set to thirty seconds or a minute, the phone locks itself while the restore is still working — which is exactly when error 4037 strikes. On the iPhone, open Settings, go to Display and Brightness, tap Auto-Lock, and choose Never. Leave this setting on until the restore finishes and the phone has fully rebooted into the home screen, then set it back to your usual value. This single step fixes most mid-process 4037 failures.
3. Update the restore software and retry. Update the restore software and retry. Outdated restore tools mishandle the unlock handshake between the computer and the phone. In classic iTunes on Windows, click Help at the top of the window and choose Check for Updates, then follow the prompts. On Windows with the modern Apple apps, open the Microsoft Store, go to Library, and update Apple Devices, the app that handles restores now. On a Mac, restores happen in Finder, so install any pending macOS updates through System Settings, General, Software Update. Restart the computer, unlock the iPhone first, then reconnect and retry.
4. If the passcode is forgotten, restore through recovery mode. If the passcode is forgotten, restore through recovery mode. Error 4037 requires an unlocked phone, so a forgotten passcode is a real blocker — but it has an official exit. Connect the iPhone to the computer, press and quickly release the volume-up button, press and quickly release the volume-down button, then press and hold the side button until the computer-and-cable screen appears. In Finder or iTunes, click Restore when prompted. This erases the phone, including the forgotten passcode, and installs the current iOS. Back up first if you have one; after the restore, choose a passcode you will remember so future updates never stall on this check.
5. Fix the USB chain and retry on a second computer. Fix the USB chain and retry on a second computer. If error 4037 survives an unlocked phone and current software, the connection itself is suspect: use the cable that came with the iPhone or another genuine or Apple-certified cable, seated firmly at both ends, plugged directly into a USB port on the computer — never into a keyboard, monitor, dock, or hub. Try a different port. If it still fails, run the update or restore on a second computer with the phone unlocked. When it succeeds there, the first computer was the problem, not the phone.
6. Handle the Apple ID Activation Lock prompt after the restore. Handle the Apple ID Activation Lock prompt after the restore. Sometimes the 4037 story ends one step later: the firmware installs, the phone restarts to the setup screen asking for the Apple ID and password, and the computer's restore process stalls. Sign in with the Apple ID that was on the phone before the restore — Activation Lock is doing its job against theft here. If you do not remember the password, reset it from another device through Apple's account recovery before retrying. Once signed in, the phone moves into the setup flow and the error clears.

Did this fix it? Quick checklist

• iPhone unlocked to the home screen before the update or restore starts, with the passcode known and working
• Auto-Lock set to Never for the whole process, then restored to your usual value afterward
• iTunes, Apple Devices, or macOS updated, computer restarted, genuine cable direct into the computer
• The phone finishes the update or restore without error 4037 — or a forgotten passcode was cleared through recovery mode

If error 4037 keeps returning with the phone unlocked, current software, and a clean USB chain, check for device management: a phone enrolled in an employer's mobile-device management can carry passcode and restore restrictions that block the process, and only your IT administrator can release them. For a personal phone that has survived every step above, book an appointment at an Apple Store or authorized service provider and mention error 4037 — it tells them the restore stalled at the unlock check, not at signing or hardware.