Scan tool recommendations

[m4rkw]

For reasons mentioned in my recent OBD thread, I don't want to use less-than-legit techstream anymore.

Can anyone recommend an inexpensive scan tool that is able to read all of the modules on a Lexus?

[Herbie]

29 minutes ago, m4rkw said:

Can anyone recommend an inexpensive scan tool that is able to read all of the modules on a Lexus?

I doubt such an animal exists.

Any scanner from about £20 will be able to read/clear engine and emissions codes but for all the modules you'll either need a very expensive one or Techstream.

You can freely and legitimately download Techstream from Toyota/Lexus and buy a block of time to use it and you can even buy a cable from them too if you're not happy with the one you've got.

You can buy a different cable from eBay and try that if you think the one you've got is dodgy.

Your auto electrician may have just meant 'don't go poking around with something as powerful as Techstream unless you know what you're doing because you can brick the car'. After all, dozens and dozens of people up and down the country are using eBay-sourced cable and software on a daily basis without problems, albeit against copyright law with regard to the software.

[m4rkw]

I don't doubt that you're right that lots of people use them without an issue @Herbie, but I don't think it would take much of a fault with such an interface to cause damage to a car. Regular scan tools operate using the pin16 12V supply from the car, so there's only so wrong they can do. Presumably if any of the pins on the OBD socket are connected to other pins on it, the system is designed with short circuits in mind so this obviously wouldn't be good but likely wouldn't break anything.

But a device that is also connected to a computer's USB bus has another source of power, and at least with the cable I have it appears these are not isolated. If I plug it into the car only - the LED lights up. If I plug it into USB only - the same LED lights up. These knock-off cables are likely made as cheaply as possible, it's not hard to imagine something going wrong in them that could then cause a problem in any of the connected car modules. I'm also told by an experienced technician that there are no fuses in the data lines, only in the power line that supplies the 12V rail to pin16.

So yeah I could get another cable off eBay and just like this one it would likely appear to work, but who knows if they can really be trusted or will be safe to use long-term.

[m4rkw]

This looks like a good contender for a quality name-brand interface that does the same thing as the eBay ones:

https://www.obdinnovations.com/vxdiag-vcx-nano-usb-j2534-diagnostic-interface-for-toyota-lexus-v13-00-022/

[Herbie]

It's your money Mark and your choice, and I respect that, I really do. However, I don't really see that there's much difference between the eBay ones and this one, except that this one is £70 more expensive.

There are no reviews so we don't know if it's good, bad or indifferent compared to the eBay ones and to just pick up on one of your earlier points, you said:

Quote

But a device that is also connected to a computer's USB bus has another source of power, and at least with the cable I have it appears these are not isolated. If I plug it into the car only - the LED lights up. If I plug it into USB only - the same LED lights up.

which is exactly the way my cable works too - but who's to say that's 'wrong'?

In the description for the one you link to, one of the features listed is:

Quote

• Power: Vehicle powered DC 9V-36V or USB DC 5V

which means that if there's an LED in it it'll light up either way, so it's exactly the same.

You obviously won't be happy with an eBay cable and that's fair enough because as I said earlier, your money, your choice. All I'm saying is that from personal experience of using my own eBay cable many dozens of times I've had no problems whatsoever, and given the quantity of these things out there being used without apparent problems, I'm more than happy to continue using mine. We'll never definitively know either way unless we could get the circuit diagrams and schematics of each device to compare the inner workings anyway.

[m4rkw]

Maybe you're right, maybe I'm just being over-cautious. There's every reason to think that the issue I had with the socket was just caused by the pins being moved out of place.

Further research on the vxdiag interface reveals:

- It can be had for about £60
- It's completely chinese-made and there doesn't seem to be a chinese web presence for the company other than a dedicated online store
- Supposedly it's much faster than the mini-vci cables, although I never found the mini-vci to be particularly slow
- Supposedly it can do stuff that mini-vci can't, such as some of the more involved programming operations which I probably wouldn't want to do anyway

I think I have to concede that you're right in the sense that there's no real reason to think that the vxdiag interface is in any way inherently "safer" than the mini-vci cable. I think I'll keep it for now and just avoid doing anything with the OBD socket unless it's necessary. I was only trying to use it the other day to program a key but I had an auto locksmith do that for me now so I have no immediate need for it.