What’s the Best Used Car Diagnostic Check?


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In the current global landscape of rising new car prices due to component shortages and supply chain issues, the purchase of a new car may not be possible. Therefore, you might consider a used car, after all, there are plenty of decent and well cared for used cars out there. However, there are also ample supplies of used cars that have been abused, poorly maintained, and have simply been dressed up, detailed and mileage fettled for the purpose of a quick and lucrative sale. As a prospective buyer, how do you detect underlying issues in a used car? This article will walk you through it, and how a used car diagnostic check can help.

Why should you perform a used car diagnostic check on a car? A used car can have underlying issues that have been temporarily covered up, disguised, or otherwise obscured in many ways. Your used car may drive normally for a week or two, before throwing up a plethora of errors and even leaving you stranded. Used car diagnostic checks are one way to detect this, and there are plenty of consumer-grade diagnostic solutions available. Our pick is Carly, a fully integrated solution that comes with some features specifically designed to check out used cars, as well as a powerful suite of diagnostic, maintenance, and customization tools.

What Should I Look Out for in a Used Car?

Used Car Diagnostic Check

Buying a used car isn’t as simple as turning up, handing over the money, receiving the keys, and driving off. That’s the riskiest way to buy a used car. We’ve written a whole article on what you should look out for in a used car.

As a refresher, you should check the exterior and interior condition, whether the car looks like it’s been well taken care of, whether it’s been recently detailed (although this on its own isn’t a bad thing), and check areas such as the footwells and beneath the trunk carpets for signs of water ingress that can signal a flood damaged car.

You should switch on the car, watch out for the indicator lights on the instrument panel, and ensure that the critical ‘Check Engine Light’ illuminates along with the other lights, before switching off. Some unscrupulous sellers simply remove the bulb from the ‘Check Engine Light’ slot in the instrument cluster to prevent it from signaling a fault. If it doesn’t light up with the rest of the indicators at start-up, something is amiss.

Taking a test drive, perusing through documentation and service records, and ensuring that the car has been subjected to all required health and emissions tests — and is in fact legal to drive on the road — are the other activities that must be undertaken.

Do not allow yourself to be rushed by the seller, if they seem fidgety or keen to quickly close the sale, it’s best to walk away. Always go to see a used car during daytime, and if it is in a garage, ask the seller to start it up and drive it out so that you can view all angles in proper lighting. A seller declining to do this is another red flag, unless they have disclosed any faults, or if the car is a non-runner and you’re looking for a project car.

What Is a Used Car Diagnostic Check?

You may be aware that any modern car has many computer control units, sensors, and wiring that controls a myriad of its systems. Identifying any issues with these systems, which include critical systems such as the powertrain, steering, braking, and safety systems can be done via a diagnostic check. Thanks to a unified interface called OBD, or On-Board Diagnostics, all cars come with the same universal port called the OBD2 port, as we are currently on the second iteration of OBD.

For those who are interested, OBD3 is in the works and has enhancements incorporated to cater to EVs and autonomous cars, but for now, you need to be concerned with OBD2. Any car produced after 2005 will have an OBD2 port to which a compatible diagnostic device or scanner can be connected, and the computer control units’ fault memories read out.

How Can I Do a Used Car Diagnostic Check?

Used Car Diagnostic Check

To start, you need to get your hands on a suitable OBD2 scanner solution with a used car diagnostic check, and we have a great recommendation for you in the next section. Once you’ve purchased an OBD2 scanner solution, it always pays off to research the make and model of the used car that you are interested in, to determine the exact location of the OBD2 port. The port is usually inside the cabin, near the steering wheel. It may be beneath the steering column, in the driver or passenger footwell, behind a trim piece, or inside the glovebox.

A seller may genuinely not know its location, or may claim to not know it if they are worried that a used car diagnostic check will reveal issues that they have been trying to cover up. If a seller declines permission to scan the car with a diagnostic device, it’s best to walk away.

What’s Your Recommendation for a Used Car Diagnostic Check?

We’re glad you asked. We proudly present Carly, a two-part OBD scanning solution. Carly consists of a hardware component called the Carly Universal OBD Scanner which, as the name suggests, is compatible with basically any car that sports an OBD2 port. The Carly Universal OBD Scanner communicates wirelessly with the Carly app that lives on your smartphone! Carly supports Android and iOS devices, and can be downloaded from the requisite official app stores.

The cost for Carly is under $100, making it great value for money, as you can use it after you’ve purchased a car as well. With regular updates and top-notch support, Carly is truly a dependable motoring partner and one that you literally carry in your pocket. The Carly Universal OBD Scanner can be left plugged into your car’s OBD2 port if desired. The Carly lite app can be downloaded for free and will tell you which features are available for your car’s exact make and model before you purchase.

What Can Carly Do?

First off, the Carly Used Car Check is a powerful option that Carly offers for anyone buying a used car. It performs a comprehensive used car diagnostic check across multiple computer control units in a target car and can accurately detect mileage tampering. Mileage tampering is thought to affect over 40% of used cars, making this a very powerful option to have on hand.

Carly’s diagnostic scanning capabilities are next in line. They can detect nearly all possible errors across most cars, and will not only present detected errors in plain English, but will use a ‘traffic light’ system to communicate if there are critical errors that must be immediately addressed moderate errors that should be addressed in the medium term, or minor errors that can be disregarded. This is important, because, to a layperson, all errors look critical, and competing diagnostic solutions do not differentiate.

For example, you may have found a great used car in super condition, and a diagnostic scan may reveal an error of ‘Climate Control Outside Temperature Sensor Malfunction’. Carly will tell you that this is a minor error and shouldn’t be a dealbreaker. Competing solutions will simply present this error, and you may miss out on a great buy, all because of a minor error that could be rectified for a few dollars by yourself.

Once you’ve purchased your used car, you can use Carly to perform periodic diagnostic checks to identify errors and keep it in peak condition. Carly also offers maintenance minders, customization through coding, and more.

Keep in mind, that every car has different software and modules built-in. Therefore specific features will vary with every model.

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