Selling a car: what a buyer will see with a scanner

The buyer will turn up with a cheap adapter. Better to know in advance what they will see — and why clearing codes before a sale is pointless.

Scanners used to belong to garages. Today an adapter costs less than a tank of fuel, and a buyer will almost certainly arrive with one. It makes sense to look at your own car through their eyes before the meeting rather than during it.

We have covered this check from the buyer's side. Here is the same thing from the other side of the deal.

What they will see in two minutes

• Active faults — the ones present right now.
• Stored faults — the ones that happened and have not yet left memory.
• Readiness monitors — and this is the interesting part.
• Live data — temperature, revs, fuel trims, voltage.

Why clearing codes before a sale is pointless

It is the first thing that comes to mind, and the first thing a buyer notices.

When faults are cleared, the car loses its readiness monitors: the unit must run all its tests again, and that takes several days of ordinary driving. Until then the app shows plainly that some tests are incomplete.

The buyer sees exactly one thing: the codes were cleared a moment ago. And what they think is not «this car is healthy» but «something was hidden from me». That signal is covered in the article on readiness.

The conclusion is simple: clearing before a sale is raising a flag. It is far better to arrive with an honest memory.

What to look at in advance

Whether there are active codes. If there are, decide whether to fix them or say so openly. A small fault named out loud costs less than one found in silence: in the second case you are not docked the price of the repair but the price of suspicion.

What the fuel trims say. Numbers far from zero point at a leak or tired injectors. A buyer who can read trims will see it.

Voltage at idle. Below 13.5 V when warm is a question for the alternator or the battery, and it is checked in a minute.

Coolant temperature. If it never reaches the working range, that is P0128 or close to it. A thermostat is cheap and the impression it spoils is not.

Stored codes. Even a fixed fault stays in memory for some forty warm-up cycles. Better to know about it and be able to explain than to be asked unprepared.

What not to do

• Disconnecting the battery before the viewing. That is clearing, only more obvious: settings are lost too, and it shows.
• Taping over the light. It sounds absurd, but it happens. A light that does not come on at all with the ignition is itself a warning sign, and an experienced buyer checks that first.
• Promising «it is only a sensor» without knowing what the code says. A code names a place, not a part — and if the buyer knows that, the conversation will go badly.

In short

• The buyer will almost certainly bring an adapter — look first yourself.
• Clearing codes before a sale is pointless: incomplete monitors are visible and read as «something was hidden».
• A small fault named out loud is cheaper than one found in silence.
• Check the trims, the voltage and the temperature in advance.
• A disconnected battery and a taped-over light are noticed and work against you.

Before the viewing itself, the whole sequence helps: how to check a car before buying — step by step, what to do and in what order.