yeshia

I have a 2012 A5 with 105k miles. I had my timing belt replaced by audi a couple weeks ago, not sure if it is related but figured I should mention it. A week later I had my check engine light come on, solid. If the light wasn’t on, I do not think I would have noticed anything was wrong. I did not have any noticeable reduction in power and was certainly not in limp-mode.

I took it to Audi, without an appointment, so they just quickly checked it and told me it was a Turbo Under-boost code. I believe it was code p0299. They told me I would need a new turbo.

Audi told me I could continue to drive without the turbo until I wanted to replace it.

I took the car and when I left I noticed the CEL was now off. Audi said they reset the code and would expect the CEL to come back on as the problem was probably intermittent. It has been about a week and no CEL.

I have a few questions:

1. Assuming it is the turbo, is Audi correct in saying that I can drive without the turbo without further damage to the car?

2. Could the timing belt replacement be the cause?

3. If the turbo stopped working, wouldn’t it be very noticeable? As I stated, I could not tell anything was wrong with my car other than the CEL light being on. Wouldn’t an underboost code put the car into limp-mode?

4. Are there other things that could cause a CEL, no power reduction and an under-boost code?

Thanks

dhayles

I had a similar problem with an A4 2.0T. You may notice that the CEL will come on if you accelerate hard up an incline. It will eventually go off if you do not accelerate over an incline in the next couple of weeks. What I found (took me a few months) was the cause was the n75 valve. It is essentially a waste gate by-pass valve for the turbo and thankfully not very expensive mine cost about $40. Installing it was a pain, while others in forums indicate it can be done after simply lifting out the cooling duct (A4 2007) I had to take off the front of the car, bumper, disconnect intercooler, drain and disconnect rad etc.