gtiwithav8

Hey all,

So I just bought a C5 (A6 Avant) and I needed to replace the cats and o2 sensors. Magnaflow cats are already in and I'm replacing the o2 sensors tonight, but what method should I use to reset the ECU? There are so many on the forums, but folks are warning about the battery method because of limp mode. I actually just replaced my battery, and didn't really notice anything different? Is my car IN limp mode now? How would I know?

I don't have a vag com, and I'd prefer not to go back to the shop, but will the battery ecu reset clear the settings/cel well enough?

Thanks all!

gtiwithav8

Also, I just read that it is easier just to disconnect the ECU. Seems the ECU is just as easy to get at as the battery was, so would this be a better method?

gtiwithav8

Okay, new o2 sensors are in. Tried resetting ECU by disconnecting battery for a couple of hours, but this didn't seem to reset the ECU... CEL still on (which might just mean new o2 sensors didn't fix the problem), but the throttle body did not go through its realignment. So I'm wondering if the ECU reset at all? Is there another method I should try to reset the ECU by?

seishuku

As far as I know, those codes are stored, so disconnecting the battery won't clear anything.
You need to clear the codes with VCDS or a scan tool.

gtiwithav8

Thanks for the response. If I want to buy my own, is this the only option?

http://store.ross-tech.com/shop/VCKII.html

Not sure if it is worth the investment/how often I'll use the thing.

seishuku

Get a $10 eBay cable and use VCDS-lite, it'll do what you need.
I can't justify the $250 cost either, even if it is worth it really.

Airbag

dont you havea buddy with an OBD2 tool ? if all you want to do is read and reset generic codes any OBD2 reader will do that ..
well at least 90 %

gtiwithav8

Yep, that did it! Thanks all! If anyone is reading this threat in the future, I would really recommend the little $12 blutooth obd2 reader.

Airbag

link ?

do you read it on your phone with an app or something ?

gtiwithav8

The one I used was the Elm327 I believe, and yeah you can use your phone as the device has blutooth. Pretty handy!