D3Audi

Alright, I'm very new to Audi and recently bought a 2008 Audi Q7 4.2 in April and its been awesome.. But this morning I went to start it and the EPC light came on and it sounded like the engine was "knocking" from inside, and on the outside there was a pulsating like squeal. Does anyone know what this could be? I'm thinking on buying one of those wifi things that work with the app "carista" to plug in and read codes.. Would that tell me what's wrong? Has anyone had anything similar to this??? What does a EPC light mean? Should j be worried and should I drive it, Also.. Should I get my wallet ready? Haha thanks!

smith2010Q7

It is your Engine Speed (RPM) Sensor (G28).
1. The Engine Speed (RPM) Sensor (G28) detects RPM and reference marks. Without an engine speed signal, the engine will not start. If the engine speed signal fails while the engine is running, the engine will stop immediately.
2. The best tool to buy is Ross-Tech: Home
3. To do the work you need this tool, which you do not have I recommend not to temp the job. For one you need to erase the codes and also need to measure the eng speed Diagnostic Mode 04.
4. It not hard, and it should only be a hours work plus part cost.

D3Audi

Okay, is that ross tool the only tool that will work? They seem a little expensive, are there any cheaper code reader things? or is that the best one. You seem very knowledgeable in this stuff! Haha!

smith2010Q7

It depends on what level DIY you are or want to be.
My best advice is to study all the youtube on Ross tech. This VCDS can get you into trouble if you do not know how to work the system.
Everyone on this form has a lot of expert advice about the Ross-Tech VCDS. Ross-Tech has there own form for info.
Audi is not set-up for US P codes, there is some but not into the level you need to know in trouble shooting the system. Audi has there own codes. (german spec)

If you not going to do your own work then do not buy just to check codes.

Hope this helps a little.