Using an ODB Scanner when buying a car...

STG.Otaku

I'm awaiting delivery of an ELM ODB II device to hook up to my car using Torque for Android. I'm hoping it proves useful enough, but I was also thinking about taking it along with me to buy a new used car.

It got me thinking if anyone else had done that? Or, if you are selling your car would you object to someone asking if they could hook up an ELM device, or similar, to your car to run a scan for any faults? Is there any security risk involved in letting someone do that?

Personally I was thinking that when the day comes that I'm in the market to buy a new car, I'd take such a device along with me and ask the owner/dealer if I could run a fault scan. I think it would be fair enough to ask. Not everyone is so well acquainted with motors that they'd know what to look for. Running a fault scan I think would help, especially if it uncovered anything there and then.

What do you think? Is it a good idea? Do you already take an ODB device with you? Would you object if someone asked to run a scan on your vehicle prior to a sale?

jimgoose

I think it's an excellent idea, and would do so myself. A quick scan for I/M status and DTCs is not a security risk, and a very useful thing to do with an as-yet unknown car.

zarquon

I have done it for every car i purchased with no issues. If someone wouldn't let me run a quick scan i'd walk away immediately.

rovoagho

I'd have no objection to someone hooking into my current car if they asked to, although they wouldn't get much since it only does blink codes. However on a newer car, there's no way in hell I'd let someone I don't know jack in. Particularly BMWs, given their recent history; and I say that as a fan of BMW.

I wouldn't have even thought of asking someone I was buying from, given the level of ignorance out there. Even dealers don't know what they're selling, never mind norms. It would only ever occur to me if I was dealing with a petrolhead.

Chimaera

I'd probably do it on a car I was seriously interested in, as part of a final check before parting with money.

How much of a security risk it is depends on what sort of scanner is being used.

If it's just a basic OBD/EOBD device, the security risk is minimal as that standard only allows for powertrain (engine/transmission) codes to be accessed and cleared. The purpose of the standard is to allow open access to powertrain diagnostics to for maintenance purposes so that emissions performance is not adversely affected.

If it's a vehicle specific tool, things get more interesting, but probably not to the point where there's a security threat. Diagnostic protocols allow access to the ECUs for repair/diagnostic purposes. Any tweaks are only possible if the protocol reveals them to the scan tool. Matching remotes and immobiliser chips typically requires at least that the key is mechanically inserted into the ignition barrel and the ignition switched on. So it'd be difficult to turn up with a key hidden in your pocket and programme it while running a 'diagnostic' on the car.

If a buyer asked me about scanning a car I was selling, I'd ask for the name of the scan tool beforehand so I could confirm its capabilities. If I wanted to scan a car I was buying I'd mention it upfront to the seller that I'd be scanning it if I'm seriously interested in the car.

Supergurrier

Did this on last car as part of final inspection or rather my much did.

Was no objections

_Kaiser_

Did this for a friend a few months back as well. Seller had no problem with it.

Lex Luthor

last car I sold the guy asked me to do a quick scan, his uncle worked for Chubb and he was proficient in using one so we took it to his place of work, plugged in and had a look...I didnt have an issue and I think it gives them piece of mind aswell
The fact his uncle was a tech in Chubb that knew how to use one made me more confident to let him plug away

Chimaera

One caveat I forgot about in my last post is that a scan can turn up old faults that have been fixed but the codes never cleared. If I'm doing a scan for someone (with VCDS) my usual routine is to scan it, save all the codes, clear them and then take the car for a drive and see what codes (if any) reappear. For a buying/selling scenario, I'd be clearing any stored codes before a long-ish test drive and see what's there at the end of the drive. Some cars can record the time/date of the fault alongside the code itself but many don't.

88manta

I done this for someone here last year.

Ended up getting 500euro off the price for him after i discovered a few things that wouldn't have been spotted otherwise.

alias no.9

I have and would run a check but the other side of it is that everybody can get their hands on these things cheaply now so how do you know that the seller hasn't just cleared the stored faults. It may be that a test drive might throw them back up but they could be intermittent in nature. Use it to rule cars out but don't let a clean bill of health pull you closer to buying a car that your gut is telling you is wrong. If it feels wrong, walk away.

jimgoose

alias no.9 wrote: »

I have and would run a check but the other side of it is that everybody can get their hands on these things cheaply now so how do you know that the seller hasn't just cleared the stored faults. It may be that a test drive might throw them back up but they could be intermittent in nature. Use it to rule cars out but don't let a clean bill of health pull you closer to buying a car that your gut is telling you is wrong. If it feels wrong, walk away.

Good point. Most faults take a few drive cycles to register as a DTC/MIL regardless.