The perfect used car finally appears on the screen for school runs and weekend adventures. It looks great, the price is right, and you can already picture yourself behind the wheel. So, you’ve found the one.
But hold on a second!
In 2025, the era of autonomous vehicles, you’re not just buying an engine and four wheels; you’re purchasing a rolling computer. It’s packed with sensors, screens, and software that make life easier, safer, and more fun. But when that tech goes wrong? It can lead to headaches and expensive bills that you don’t want.
So, identify a product before it’s too late? You should run the proper checks. In this blog post, I have listed the 10 essential tech checks you absolutely must do.
10 Tech Checks Before Buying a Used Car in the UK
1. The Pre-Check: Run a Full Vehicle History Report
Before you even dream of a test drive, the single most important check happens right here, on your laptop or phone. Honestly, if you ignore everything else in this guide, don’t ignore this. Using the best service for car history checks online is your first and most powerful line of defence.
Think of it like checking someone’s references before hiring them. It reveals the car’s digital ghost—the history the seller might ‘forget’ to mention.
What does it check?
- Outstanding Finance: Is there a loan secured against the car? If so, the finance company legally owns it, not the seller. You could buy the car and have it repossessed with zero recourse. Yikes.
- Stolen Status: Is the car listed as stolen on the Police National Computer? This check stops you from buying a car that doesn’t legally belong to the seller.
- Mileage Discrepancies: It compares recorded mileage from various sources (like MOTs) to see if the odometer might have been wound back.
Skipping this is like playing roulette with thousands of pounds. It’s the smartest tenner you’ll ever spend when buying a car.
2. The MOT Deep Dive (Not Just the Certificate)
“It’s got a full year’s MOT!” is a classic sales line. Great. But that piece of paper only tells you the car was roadworthy on one particular day. The real gold is in the car’s full MOT history, which you can check for free on the government website.
Don’t just glance at the pass/fail results. You’re looking for patterns.
- Recurring Advisories: Did the same issue (“slight play in front nearside wheel bearing”) appear as an advisory for three years running? It means the owner has been ignoring a developing problem that you will likely have to pay to fix.
- Failure Forensics: What did it fail on? A recurring failure for “exhaust emissions” could point to a much deeper engine problem than a simple sensor replacement.
- Mileage Jumps: Does the mileage log look sensible? A big, unexplained drop could be a sign of clocking or a data entry error you need to question.
3. The Infotainment Gauntlet
This is the fun bit, but don’t get distracted by the shiny screen. You need to put the infotainment system through its paces like a drill sergeant.
- Screen Test: Is the touchscreen responsive? Or does it lag like a dial-up modem? Dead spots on a screen are common and often indicate a need for a whole new head unit.
- Connect Everything: Pair your phone via Bluetooth. Does it connect easily? Make a call. Does the person on the other end hear you? Stream some music.
- Sat Nav Sanity Check: If it has built-in sat nav, input a destination. Does it find a signal quickly? Are the maps ancient? Map updates can be surprisingly expensive.
4. The Driver-Assist Reality Check
Modern cars on an array of sensors and cameras in the bumpers and windscreen with a designed system. A small knock can throw them out of whack.
During the test drive, try to test them safely.
- Parking Sensors & Cameras: Check the sensors beep when you get near an object. Is the reversing camera image clear, foggy, or flickering?
- Cruise Control: Get on a clear, open road and activate it. If it has adaptive cruise control, see if it works smoothly.
- Lane Assist: See if the lane-keeping assist function gently nudges you back into line, on a road with clear markings.
If these systems are faulty, they can be complex, costly to recalibrate or repair, and cause inconvenience.
5. The Dashboard Warning Light Gamble
Turn the key to the ignition position (without starting the engine). A whole galaxy of lights should appear on the dashboard. This is the car’s system check.
Now, start the engine.
Every single one of those lights should go out within a few seconds. If any light stays on—especially an engine management light (the one that looks like an engine outline), an ABS light, or an airbag light—you have a problem. Don’t accept “Oh, it just needs resetting.” The reason for that light could be anything from a £50 sensor to a £2,000 DPF (Diesel Particulate Filter) issue.
6. The Climate & Comfort Check
Don’t just assume the heating and cooling work. Test them properly.
- Air-Con: Turn the Air Conditioner to its coldest position and full fan speed. You should feel proper cold air coming through the vents within a minute. If it’s just cool-ish, it probably needs a re-gas at best, or a new compressor at worst (£££).
- Heaters: Crank the heat up. Check it blows hot.
- Heated Everything: If the car has heated seats, a heated steering wheel, or a heated windscreen, turn them all on and wait a few minutes. Make sure they get warm.
7. The VIN Mismatch Test
The Vehicle Identification Number (VIN) is the car’s unique 17-digit fingerprint. It’s usually stamped on at the base of the windscreen and on a sticker inside the driver’s door jamb. and recorded in the V5C logbook.
They must all match. Perfectly.
If they don’t, run away. It’s a major red flag that could indicate the car has been stolen and given a new identity (“cloned”) or has been in a major accident and pieced together from other vehicles
8. The Key Question
Does the car come with two keys? It should. Modern car keys are complex bits of tech with transponders that talk to the car’s immobiliser. Getting a replacement program can cost hundreds of pounds.
Test both keys. Make sure they both lock, unlock, and start the car. If it has keyless entry, walk away from the car with the key in your pocket and see if the doors lock automatically (if they’re meant to), then check that you can open the door just by touching the handle when you return.
9. The “Hidden” ECU Scan
This one is for the truly dedicated, but it’s the ultimate tech check. The Engine Control Unit (ECU), stores error codes for faults that might not be serious enough to trigger a dashboard warning light.
A seller might even clear the codes just before you arrive, so the dashboard is clear, but the underlying problem is still there.
The only way to find these is with a diagnostic scan tool that a good mechanic will have. If you’re serious about a car, getting a professional pre-purchase inspection is a brilliant idea. They will plug in and read the car’s mind, uncovering any lurking gremlins.
10. The Software Update Query
Modern cars function on complex software that often needs updating to fix bugs and improve performance. Ask the seller if the car’s software has ever been updated at a main dealer. For some brands (like Tesla and Polestar), updates happen automatically over the air. For others, it’s a manual job. Software without updates can cause glitches with the other systems. It’s a fair question to ask and shows your awareness.
Final Thoughts
Buying a used car doesn’t have to be a gamble. With these 10 tech checks, you’ll be equipped to spot red flags, ask the right questions, and make a smart purchase. Whether you’re eyeing a city hatchback or a family SUV, a little diligence goes a long way.
Ready to hit the UK’s roads? Just make sure your next ride is as reliable under the bonnet as it looks on the outside.
