The symptoms ESP issues present themselves in the following warning lights on the dash, no ABS, no ESP, no hill start assist and disabled cruise control.

ESP and ABS warning lights on the dash can be attributed to a number of causes. If you are able to analyse the fault using a code reader this will really help to narrow down the issue. If the fault is connected to the rear wheels check the ABS reluctor rings for any damage first. If these appear ok, then the problem is likely to be electronic. If you have access to an MB Star, this will indicate the particular wheel at fault. It may also suggest replacement of the sensor itself - this is highly unlikely to be the cause.

The wiring to the rear ABS sensors was badly routed when installed at the factory. Over time, this wiring may rub against other parts and suffer damage. In order to assess the wiring and perform a good quality repair, you will need to remove both sections of the undertray. Locate the ABS pump / ESP controller which is on the left hand side of the car near the front.

With the undertray removed, two points of damage were immediately obvious. The wiring loom to the rear wheel sensors is pulled very tight from where it connects to the ESP controller. This resulted in the loom wearing through where it presses against the ABS pump casing and also where the it was in contact with a sharp edge on the undertray.

 A closer view of the damage from the ABS pump casing:

To repair the loom, unplug the two connectors to the rear sensors. Each connector has a different pattern so you don't have label which plug connects to which socket. Carefully cut the cable ties which hold the loom to the brake pipes.

With the loom free, you can closer inspect the damage and perform a repair.

With the outer PVC tape removed, the break in the wiring was obvious. This was the wear from the undertray. The damage from the ABS casing hasn't warn through the cable on this particular car.

Repair the loom using an inline splice. We recommend wrapping the entire loom in a water proof wiring loom tape such as Tesa tape.

Tie the wiring back to the cable supports clipped to the brake pipes. Start from the ESP controller and ensure that the loom is routed comfortably without tension.

We find that routing the loom to the left of the ABS pump provides comfortable clearance and avoids any chance of the wiring being damaged from either the pump casing or undertray.

Finally, reconnect both sensors.

The ESP and ABS warning lights should go out automatically. However, we recommend having the fault codes read and cleared using a diagnositics set. All ESP/ABS functions will resume once the fault is cleared.