C003E: Versorgung des Raddrehzahlsensors hinten

The rear axle wheel speed sensor supply circuit has a fault.

A supply fault is not a sensor fault, and this is the code that says so.

The module feeds its sensors a regulated voltage, and that feed is usually shared. So a supply fault can take out several sensors at once while every sensor is perfectly healthy — and the give-away is exactly that: more than one corner reporting together.

Read every stored code before touching anything. One corner is a corner problem; two or more sharing a supply is a supply problem, and replacing sensors one at a time is how that diagnosis becomes expensive.

A wheel speed sensor and the ring it reads are two parts, and the codes distinguish them.

The sensor is a fixed pickup; the tone wheel is a toothed or magnetically striped ring that turns with the hub. The sensor counts teeth going past. So an identical symptom — no signal, or a signal that goes wrong at certain speeds — can come from either half, and replacing the sensor when the ring is at fault is one of the commonest wasted repairs on this system.

Look at the ring before buying the sensor. Rust swelling under a pressed-on ring, a cracked ring, a tooth knocked off during a hub or driveshaft job, or dirt packed into the teeth all produce sensor-shaped faults. Iron dust clinging to a magnetic sensor tip does the same and wipes off with a rag.

A worn wheel bearing belongs on this list too, because many sensors are built into the bearing and because play at the hub changes the gap between sensor and ring as the wheel turns.

The most important thing first: the car still stops.

ABS, traction control and stability control are all additions to a braking system that works without them. When the module finds a fault it switches itself off and hands back a conventional, fully hydraulic brake system — the pedal, the master cylinder, the lines and the calipers are untouched. You have not lost your brakes.

What you have lost is the help. Without ABS the wheels can lock under hard braking, which lengthens the stopping distance on a slippery surface and — the part people forget — takes away your ability to steer while braking hard, because a locked wheel cannot generate cornering force. Without stability control the car will not catch a slide for you.

So drive it, but drive it as though it were forty years old: brake earlier, leave more room, and be especially careful in rain, snow and on gravel.

This is an axle-level code, not a corner. Where the four corner triplets each name a side, C003C–C003E name the rear axle as a whole — a single sensor reading a ring on the differential or the propshaft, as fitted to vehicles that measure the rear axle once rather than each rear wheel. A car has one arrangement or the other, so these codes and the per-corner rear ones are alternatives rather than a set.