EPC light - 2007 A4 2.0T
 

After doing all kinds of research on this EPC problem, I thought I would run this by the forum and see what everyone thought. It seems there are a lot of un-answered questions to the cause of the EPC issue. Especially when it regards the P0243, P0444, P2294 and P2400 codes. Almost everytime I have seen these with vag-com data, it is when the auto is a zero speed. At least, this is the case with mine. It doesn't make sense that the devices related to these codes would all be defective. Since the error appear to occur right at starting, I begin to wonder about a low voltage issue causing some flaky things when starting. I checked my battery with no load and it was about 12.65v. With the key on, it dropped to about 12.2v, then on starting I saw it dip to 10.55v. Last night it was relatively cold, about 30deg and the car had not been cranked all day. I would expect a slight weak battery. A couple of minutes after starting it, I got the EPC light and went into limp mode. Cut it off and on several times and EPC still would not go out. Decided to drive it a couple of miles to get it warmed up. Stopped and restarted and the light went out. This little amount of time would allow the battery to get a little more charge and maybe not trigger the EPC upon restarting. Just a theory that maybe a slightly weak battery with a low voltage on starting might be the culprit.