#QOTW 91 – Pre Purchase inspection: Should I buy a car with these fault codes?

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Welcome to Bamford Rose and another question of the week. This week it’s “should I buy this DBS with these fault codes?” So this comes from a pre-purchase inspection that we did on a 2010 era DBS. Now the car was pretty mint and from looking at the condition of the exterior paint work and the interior, the mileage it’s service history, it was definitely one to go for. Now, when we arrived, we thought that this pre-purchase inspection was just going to be box ticking because it really did the look, a good car. Price was right, everything was good about this DBS. The pre-purchase inspection revealed nothing out of the ordinary. The odd bits of consumable were that most of them had and always looked good until the final bit of the pre-purchase inspection, which is the diagnostic laptop check. A pre-purchase inspection is a bit of detective work to understand what’s going on in the car and make sure that the car is harboring nothing. And you have to go to the lens of being a detective, because some people do try their hardest to conceal stuff.

So when you plug in and you read the fault codes and get no errors whatsoever, that’s all great. But you know, we need to dig the surface a little bit deeper. What we do is unplug typically a throttle body connector, and then turn the ignition on. Now that is going to generate a fault code for the throttle body, which the energy management system can no longer see, but we’re not interested in that. What we want to do is we want that serious fault code to trigger the freeze frame data. So this is the snapshot of data that the engine management system takes when a serious electrical malfunction has occurred. As you can see from this screenshot, you get a list of parameters. And what we’re interested in looking at is one that’s quite close to the bottom there, which says the number of engine warm ups since the fault codes were last reset.

Now, in this case, it’d only been warmed up six times since someone has reset the fault codes and the line underneath that is how many kilometers it’s traveled since that last fault code read. So what we should be seeing is that the number of kilometers recorded here is the same as when the last service was performed, because that should really be the last time that the laptop went on the car to reset fault codes. But if like this car, we can see that it’s traveled a very short distance and only warmed up a small number of times since the fault codes were last reset, then this is an alarm bell. So after that we test drove the car and the garage that was sort of chaperoning us and administering a sale was quite reluctant for us to test drive the car.

They only wanted it rounded the industrial state, where they were based, didn’t really want us to go out on the highway. Around that industrial state. It then triggered a transmission for code, which is this one pictured on the list here. Now this is a fairly nondescript code P0705 and that could be a range of issues. Obviously, all the codes underneath that are because we disconnected the throttle body and that’s generated some codes, which the system displays now. It turned out that this car had a history of the transmission code here being reset. And it was only this level of detective work, which uncovered the problem which caused the vendor to sort of come clean, that they’d been resetting this fault code for quite a while, had that fault, not been found by performing the little trick that we do during the pre-purchase inspection.

Then this would have been one of those classic cases where the used car salesman sells the car perfectly for free. And then out here should very shortly into new ownership there’s a fault that keeps developing and triggering fault codes. Just goes to show that the level of detective work on the electronic side of a pre-purchase inspection is just as important as the mechanical investigation. Because the vendor couldn’t provide a satisfactory fix to this problem, then the customer that we performed the pre-purchase inspection for this car bailed on that purchase. Unfortunately it takes the AMDS kit, the official factory, or the laptop, a diagnostic kit to perform that little trick and someone generic performing a pre-purchase inspection. Isn’t going to go, or isn’t going to be able to go to that level of detail unfortunately, meaning really only independence with the AMDS diagnostic kits can perform a pre-purchase inspection to the level needed. Hope you enjoyed that question of the week and we’ll see you on the next one.

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