Description
Every B8-generation Audi A5 (2011–2018) — coupe, Sportback and Cabriolet alike — steers through an electromechanical rack, with the assist motor and its control electronics mounted on the rack rather than fed by a hydraulic pump. When that control side fails, the dash shows “Steering defective! Do not drive vehicle!” and the A5 loses its assistance. We take the failed rack in, put it right on the bench and return the same unit to your car.
Which A5s this covers
The listing is for the B8 A5, chassis codes 8T and 8F, built between 2011 and 2018. The fault and our repair are the same whichever of the three body styles you drive, so one listing covers them all.
Labels still vary by build. Control-unit numbers we commonly see across this Audi rack family begin 8K0 909 144, 8R0 909 144 and 4G0 909 144 — for example 8K0 909 144 E, F, G, J, P or R. We do not assume which applies to your A5: copy the number from your unit onto the repair form so it can be matched before work starts.
What the warning and codes are telling you
The red message means stop — have the car recovered rather than driven on. It is sometimes preceded by a yellow steering-wheel warning that clears and returns, and it tends to arrive alongside heavy steering at parking speeds, a wheel that will not self-centre and, on some cars, a refusal to start.
Two codes dominate a scan of a failing A5 rack: C10AD29, logged against the motor position sensor, and B200049, an internal control module error. Neither implicates the tie rods, column or loom. Both are raised inside the rack’s own control unit, which shuts assistance down the moment it stops trusting its motor data.
Why moisture finds the A5 rack
On the A4 and A5 the rack sits a little higher than on the A6, but not high enough to keep water out once its seals have aged. Moisture that gets inside reaches the electronics, and heat and vibration over the miles finish the job. The mechanical rack is typically still in good order when the electronics give up — which is exactly why repairing it makes sense.
Your own rack, or a replacement?
Going new or exchange means finding a rack that matches your A5’s exact build and, on an exchange, returning your old one as a core. Sending us the rack already on the car removes the matching question altogether, because the unit that comes back is the one your A5 was running.
Your garage removes it and posts it in. We diagnose it with dealer-level tools, carry out the repair in our cleanroom-standard, ESD-safe workshop, and load-test it on our Hardware-in-the-Loop rig before it goes back. Most of our remanufactured parts carry a lifetime, unlimited-mileage warranty.
Booking the repair
After checkout, print the repair form, fill in the symptoms, any codes and the label number, and put it in the box with the rack — or post the form ahead of the unit. Either way, your A5 rack is ready for the bench as soon as it lands.
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