Originally Posted by Muppetir

My limp mode saga continued for 2 months. If you're encouintering limp mode and have a damp footwell carpet this maybe worth a read. After changing a few parts and the problem re-occuring intermittently I deduced it only went into limp-mode in wet conditions. (No sh=t Sherlock)

Turned out a replacement wiper motor fitted months before required the ECU unit to be unscrewed and moved back a few inches to allow the wiper motor to be removed and replaced. Moving the ECU had dislodged the rubber gasket beneath the ECU unit. It's almost impossible to see.

This misplaced rubber trim allowed the elements in. Rain water from the windscreen was washed down through the drainage chamber at the rear of the engine around the battery bay, through the gap under the ECU, down the throttle cables to the throttle sensor, throttle assembly etc. This caused circuits to short out, throw up 'COIL' and 'ESP' alarm and car went into limp mode or often totally lost all power.

3 trips to Audi and no joy, and finally 3rd AA man felt water coming down the throttle cables as it was raining while he inspected car.

I removed ecu unit using a torque set, felt under the ecu and pushed rubber gasket back up into the 10mm edge gap around the whole underside of the ecu. When the ecu is refitted the rubber acts as a water tight seal.


You can see better (But not reach) if you remove dash board cowl under steering wheel and shine torch up to the right where the ecu is.

One rubber seal, thousand pounds, mis-spent thank you sir.