Checking a used phone before you hand over the money
Most of this site is about fixing devices after something has gone wrong. This one is about the cheaper option: spotting the problem before you own it.
These are the checks I would run on any used phone, in the order I would run them, with the reasoning for each. Ten minutes, no tools beyond the phone itself.
1. IMEI, and the check most people skip
Dial *#06# on the phone itself. Not the box, not a number the seller reads out — the phone.
In Pakistan, send that number to 8484. Then do the part almost everyone misses: compare the brand and model in the reply against the device in your hand.
A registered IMEI record includes the make and model it belongs to. A patched device reports its own real hardware while carrying somebody else’s number, so the two do not match. Reading only the word approved tells you nothing; the mismatch is the giveaway. The full mechanism is in the article on IMEI patching.
Check both IMEIs on a dual-SIM phone. And if a seller discourages you from doing any of this, you already have your answer.
2. Software state
Several things worth knowing before you buy:
- Is it running stock firmware? Settings, About phone. An unfamiliar build number or a custom ROM name means the device has been flashed.
- Is the bootloader unlocked? Many devices show a warning screen at boot. An unlocked bootloader is not automatically bad, but it is a reduced security posture and some banking apps detect it.
- Is it signed into someone else’s account? Factory reset it in front of the seller and confirm it completes setup without asking for their credentials. A device that demands the previous owner’s account after a reset is a device you cannot use.
That last check is the single most valuable one on this list, and it takes five minutes of waiting.
3. Hardware, quickly
- Screen — a full-white and full-black image reveals dead pixels, burn-in and discolouration that a home screen hides
- Touch — drag a finger across the entire surface, edges included
- Cameras — every lens, front and back, checking focus
- Microphones — record a voice memo, then make a call. Different paths, and one can work while the other does not
- Speakers — earpiece and loudspeaker separately
- Charging — connect a charger and confirm it actually draws
- SIM and network — insert a SIM and confirm it registers, not just that signal bars appear
- Sensors — rotate the device for auto-rotate, cover the top during a call for proximity. Broken sensors often mean a wiped persist partition rather than hardware damage
4. Storage and battery
Two things that are not visible in a quick look and cost real money later.
Storage. Copy a large file onto the device and open it. Failing eMMC often passes casual use and fails on sustained writes. A device that has been through repeated flashing has had more write cycles than a normal one.
Battery. Note the percentage, use the device actively for ten minutes, note it again. A battery dropping several percent in that window is near the end of its life. Factor a replacement into the price rather than discovering it a week later.
5. Physical signs of previous repair
- Gaps or uneven seams between the screen and frame
- Adhesive residue around the edges
- Damaged or rounded screws
- A screen that flexes or clicks under light pressure
Previous repair is not disqualifying — I repair devices myself. But it should be disclosed, and it should be reflected in the price. Undisclosed repair tells you something about the seller rather than the phone.
Frequently asked questions
- What is the single most important check?
- Factory reset in front of the seller. An account-locked device is unusable and the lock is not removable by any legitimate means.
- The price is well below market. Is that always bad?
- Not always, but understand why. On an unregistered or patched device, the discount is usually the unpaid duty — which becomes your problem when it stops working.
- Can I check whether a phone was stolen?
- IMEI verification will show a blocked status for a reported device. It is not comprehensive, but it catches the obvious cases.
- Is a phone with a custom ROM a bad buy?
- Not necessarily — but confirm what it is running and that you can return it to stock if you want to. Ask for the model number and check that stock firmware is actually available.
- How do I check storage health properly?
- Without root, large file copies and sustained use are what you have. Slowdowns and failures under sustained write are the warning sign.
Seen something on a phone you are considering and not sure how serious it is? Describe it with the model number. Some faults are cheap fixes and some are the end of the device.