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Q: EPC Light is on - 2011 Audi A4

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When I power on my car it starts shaking. I saw it is because the engine shakes a lot. The issue started 2 days ago, I was driving for 5 minutes, then the Check engine light started flashing then the EPC light got On. I had trouble to accelerate. I decided to go back home and park the Car. Yesterday I turned my car on again. The engine starts shaking in the same way. Then I turned it off.

My car has 70000 miles.
My car has an automatic transmission.

A: Hi there. While driving the vehicle and hav...

Hi there. While driving the vehicle and having the engine light begin to flash, then there is a major problem that is currently existing. When the EPC light comes on, there is an issue with the throttle pedal, throttle body, traction control, or cruise control.

Due to the nature of the engine shaking while both lights are on, this would be due to a loss of fuel or a high volume of fuel to the cylinders. Most likely, the throttle pedal has lost communication to the computer and the computer is trying to determine what the count is on the pedal. This put the engine into a limp mode and make the fuel system either go lean or rich depending on the counts on the throttle pedal.

Unplug the harness to the pedal and put a digital ohm meter on the terminals to the pedal. Check resistance on the pedal with it up and then check resistance with the pedal down. If there is no change, then the throttle pedal needs replaced. If there is a change, then the throttle position sensor needs replaced on the engine.

If you need further assistance troubleshooting your vehicle, then seek out a technician, such as one from YourMechanic, that can perform these tests and properly diagnose rough running engine at your own location.

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