Car ODB2 diagnostic tools for VWs.

[Michael Chare]

I would like to buy a car ODB2 diagnostic toool suitable for use with European VWs. I don't need compatibility with other makes. I want something that has full diagnostic and update facilities rather than the cheaper ones that can just display some details.

I have found some devices that don't have a display but connect to a smart mobile phone running an app using bluetooth. One such device would only work with American VWs and required to keep buying a licence for the app to work.

One tool I have found was an iCarsoft VAWS V3.0.

Can anyone suggest an alternative?

[Andy Burns]

VCDS is the de facto tool for all VAG cars

ross-tech have changed the licensing since I bought mine, and audi have added extra comms lines too, so there are a couple of modules which my lead can't handle in my current car.

Of course others exist, search youtube or a forum such as VWAF

[Michael Chare]

Thank you for the reply. Do these tools show when a car battery is about to fail and is it necessary to update the car if you change the battery?

[SH]

Yes, you need to tell teh ECU what type of battery is on the car, think there is AGM and something else.....

So you will need to look what it says for the original battery, if you do replace it, you do need to tell it what the new battery type is.

[Andy Burns]

I think it can give a certain amount of battery voltage history, I can't check because the mild-hybrid system is one of the modules my older lead won't touch. In general it can code for battery replacement ...

[Tim Lamb]

This cropped up here a few months back. Clearly if the car has auto stop/start you need a suitable battery type. It was suggested that the battery needs to be registered so that the car electronics can match the charging rate to the expected battery performance. I decided to not bother on my VW Passat as the minimum charge here for a garage to hook up the diagnostics is £60 or half the cost of a new battery! I have a Chinese £60 analysis tool which has sorted out an ABS sensor fault and told me to replace my glo plugs:-)

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[The Natural Philosopher]

Indirectly, yes. You tend to get plethora of 'low voltage' warnings. from various places. Its far better to take the car into a battery service place and get it tested for internal resistance and voltage

and is it necessary to update the car if you change the battery? For some cars, yes.

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[Michael Chare]

Until I started looking into ODB2 tools I had not idea that I might have to tell the car about a battery change. I replaced the AGM battery in a

1.5 diesel VW Jetta with a new one of the same type some months ago. I noticed that my 2.0 diesel Passat uses the same battery!

When I am at home it does not matter if the battery goes flat, I just use the other car to get a new one. I once charged my car battery, drove it to Halfords to buy a new one, then had to fit it outside Halfords to start the car to come home.

My present car keeps telling me that the rear left tyre is flat. It turns out that the rear ABS sensors are the same on both sides so I might clean the contacts and swap them round and then see if I get the same error on the right rear. If so I will buy a new sensor.

[The Natural Philosopher]

It could be that the tyre is more worn, or of a different make

[Joe]

Note that for many cars it is necessary to shut all electronic systems down before removing the battery. I knew someone who killed the computer of a Peugeot xyz (can't remember which one) by just changing the battery in what used to be the usual way.

We thought the Peugeot dealer was winding us up about this, but no:

[mm0fmf]

Perhaps it was worried about having to work longer before it got its pension and went on strike and trashed the ECU.

[Michael Chare]

I looked in the handbook for my car and it just says to switch everything off before disconnecting the battery. Not that I read that before the first time I disconnected the battery because I wanted to work on the electrics. (Fitting a box which connects to the canbus and supplies power to the trailer lights socket.)

[RJH]

I read about that after I changed the battery on my 2015 Peugeot. Luckily I got away with it . . .

[Joe]

I think it's a matter of luck as to whether writing is going on and if everything is in a consistent state. A bit like pulling out a USB stick without dismounting it, when there may be cached data not yet written.

Apparently the ECU in this case was not actually physically damaged, it just needed the equivalent of reformatting, at a cost greater than the value of the car.

[mm0fmf]

It's not like that is something the designers could have designed for!

Having worked as a software bod on a lot of VAG ECUs, they all have 2 copies of the FLASH memory. An A and B image. The system will boot from one and keep the other as a spare. If it can't boot, or there is a boot time CRC fault it uses the other image from then on. Software updates are written to the not-in-use image and a test boot is made. If that works then the system restarts using the new written image. After a number of successful starts the new image is copied to the other image and the process of using image A or B starts again.

Similar processes are used for saved parameters so they too can be guarded against corruption and glitches in use.

[Rod Speed]

Corse it is, don't allow writing when the supply voltage is too low.

[Alan J. Wylie]

I have an Ancel VD500. It's VW specific, shows a lot of status codes and cleared the fault I needed it for (dodgy connection in the air-bag disable switch in the glove box was very occasionally causing an orange light on the dashboard).

All-in one with LCD display, software updates available over USB.

Available on eBay from £40

[Mike Rogers]

This one works to delete codes on my wife's 2016 Yeti