Audi A6 (2011 – 2018) Electric Power Steering Rack

A “Steering defective! Do not drive vehicle!” warning on an Audi A6 C7 (2011–2018) is almost always the electric steering rack’s own control unit failing. The assist motor and its electronics are part of the rack — there is no hydraulic pump — and on the A6 that control unit sits very low, close to the road. We repair the original rack and return it to your A6, rather than supplying a new one that sits in the same exposed spot.

Why the A6 is prone to this fault

Position is the problem. On the A6 the rack’s control unit is about the lowest point above the road, so even a small breach in the seals lets water reach the electronics. Heat and vibration then do the rest, and it is the control side, not the rack and pinion, that typically fails first on a high-mileage car.

Warning signs and fault codes

Alongside the red cluster message — which means the car should not be driven — owners report heavy, unassisted steering at low speeds, poor self-centring and a warning that comes and goes before it stays on. Some A6s will not start while the fault is active.

Scanned, the rack usually shows C10AD29 (motor position sensor) and B200049 (internal control module error). The control unit raises these when it stops trusting its own motor data, and it shuts assistance down in response. Neither code points at the column, tie rods or wiring.

Is this the right rack for your A6?

This repair is for the C7-generation A6, chassis code 4G, built 2011–2018, which uses an electric rack. The earlier C6 uses a hydraulic rack, so this listing does not apply to it.

Control-unit numbers we commonly see across this Audi rack family include 4G0 909 144 J, K, L, M, R, S and T, alongside 8K0 909 144 and 8R0 909 144 variants. Check the label on your unit and write the number on the repair form so we can match it to your car.

Repairing yours versus buying a replacement

• Replacement: a different rack that has to be matched to your A6’s build, with an exchange unit usually requiring your old rack back as the core.
• Repairing yours: the rack that comes back is the one already fitted to your A6, so there is no matching exercise and no core to return.

Your garage removes the rack and posts it to us. We diagnose and repair it in our cleanroom-standard, ESD-safe workshop, then test it on our Hardware-in-the-Loop rig under simulated heat, vibration and steering load. Most of our remanufactured parts carry a lifetime, unlimited-mileage warranty.

Sending the rack in

After checkout, print the repair form, complete your details and the label number, and include it in the box with your A6 rack — or send it ahead of the unit. With the form in hand, your rack is logged and ready for the bench the day it arrives.