Got an 2014 Audi S5 V6 supercharged version CREC engine 34k miles on the clock. Recently developed a weird fault. Driving normally without putting my foot down or when parked the engine runs perfectly no misfire or any knocks or weird sounds coming from engine bay. I can even rev the car to the soft limiter when parked without issue. However when driving, even if I slightly further press the accelerator/gas pedal, EPC light comes on, the car jerks until I come off the accelerator but then sounds like it's misfiring. Begins rev hunting (rev climbing then going back down without any input to accelerator). Engine begins to sound rough and a strange slight knocking sound begins to come from the engine bay. Plugged a computer in and error P069800 shows which is to do with voltage error on circuit c. A mechanic has had a look at it, changed spark plugs but to no avail. New coil pack and battery ordered for the car going in on Wednesday but I'm wondering if anyone has any info or suffered from the same or similar thing. I've only had the car 3 week's and haven't been able to enjoy it properly. Car has some mods, a Canadian auto performace intake and x pipe with the tips on the back box being changed but I can't think either of them would cause this error. Mechanic has a look at intake and confirmed it has been installed correctly. If anyone has any advice I would be very grateful. It's booked to be seen by a auto electrician but that is some time away and ideally I would like the car to be fully driveable by the end of the month.

 

If you have a good scan tool, ie VCDS or similar, you could log misfires, knock sensors, air/fuel ratio/corrections, O2 sensors? The shop manual says you need a new ECU but sometimes it can be a bad sensor supplying the information but the only way to more easily figure it out is to data log as many channels as you can find and try to narrow down the culprit. That is an unusual code.

 

^ Listen to this guy. He's good.

But whilst i am here. .

You say it's only when you want to load up the car for a quick "rush" when driving?

First thought is the Intake. If it isn't Tuned for it?
Your car will take a massive gulp of air (possibly warm air) , And not have the fuel / spark to match. Essentially running lean. And the ecu is trying to find a fix.
So the code might mean "ECU is confused when you load it up". - Air to fuel ratio's are way off. (could be a related sensor)
You said you already ordered Spark parts. So you should be good there. Check fuel pressure. And related stuff, like the pump and fuel filter.
With Spark and fuel OK?
The Air is the problem. Any chance you can try it with an original air intake system? Then restart modding with the bits You have, properly?

Just thinking out loud. Hope it helps.
L.S

 

Thank you to both for the replies. Car does have a intake fitted on it but was fitted as soon as I bought it. It only recently started doing this. Got a new battery and coil packs going in today, mechanic said the battery fitted at the moment is too small for the car so maybe the issue. Already changed spark plugs didn't solve the issue. Hoping today new battery and coil pack will fix it.

Have suggested to mechanic to drive it whilst a computer is connect to see exactly when/what rev the code comes up. Will keep you guys updated.

 

No problem. happy to help.
But if the battery already fitted did it's job to crank start it? and the Alternator did it's job to keep up the power? watch the voltage when loaded up. I Doubt it will drop. you need some air resistance. same as back pressure in the exhaust.
So if you want to run the new air intake? Run a bit more boost and match the fuel. for efficient combustion. consider an ECU tune/ fuel system. The whole lot. should be scary fast.

 

There is an older thread on Audizine concerning batteries. A battery smaller than stock can cause faults & limp mode. I am in that thread and had it happen to me. I installed a small Lithium battery and got the faults. I still have a Lithium battery but have a larger one and all is fine now. It is part of what is call "recuperation". Under hard acceleration the car will stop charging then under low acceleration or off throttle the car will try to overcharge slightly to make up for it. With me I think I tried a 36Ah battery and swapped to a 60Ah battery, both Antigravity brand. The 36Ah battery started the car fine. The 60Ah battery still only weights 21lbs compared to the stock batteries 56lbs. You can disable the recuperation by unplugging the lBEM wire that is on the Negative lead to the battery.
https://www.audizine.com/threads/lis...atings.915905/
https://forums.audirevolution.net/t/...-rock/16501/20

 

That's interesting. and good advice.

Hope the O.P gets it working right.

 

Fitted new battery, got a genuine Audi one. Faultless for few and then again the error came up. But now also a mechanical error stating supercharger intake regulatory flap has malfuntioned. Looks like the car will still be spending some time in the garage.

 

Quick update,

The garage I took it to had a A5 with a similar fault where the water pump was leaking and corroding some wires right underneath. So got the water pump thermostat and PCV valve replaced but problem still persisted. But another error came up about mechanical fault with the super charger bypass valve. Replaced bypass valve and all faults went away and the car began driving once again as normal. However literally a day later it has developed another fault. ESC light has come on, steering light has come on and the MMI has no power and none of the MMI switches have any light behind them. Could this be linked to the original fault or is this a seperate fault developing all together? Honestly this car has been such a gremlin I fell like just setting it on fire now.