Harness With Relay & OVERVOLTAGE Protection

On E320 and E500, ABS system includes a supplementary harness. Power is supplied by a relay that is controlled by ignition switch. An overvoltage protection unit, located inside relay, protects electronic control unit. The harness is connected to control unit by a 35-pin plug. The 12-pin plug harness leads to hydraulic unit. Ground cable for hydraulic unit is mounted to inner fender well. On E420 power is supplied via the basic module which contains fuses for circuit protection.

Front axle speed sensors connect to harness by coaxial cable. Speed sensor cable from steering knuckle-to-coaxial cable routes through tubing to bracket on firewall and through inner front fender well.

Rear axle speed sensor connects to harness under rear seat by a cable connector. See Figure . Two relays are located under hydraulic unit cover. One relay controls return pump, and the other relay sends current to solenoid valves. Diode in plug socket lights instrument panel warning light when multi-pin plug on control unit is pulled off.