E-Mas Steering Management Module Actros

The A0004460420 is an electronic control unit dedicated to managing auxiliary axle steering on Mercedes commercial vehicles equipped with a steerable third axle. It is commonly referred to in the aftermarket as the E-MAS / EHZ module and is integrated into the electro-hydraulic system that controls the angle of the auxiliary rear axle based on speed, steering wheel angle and vehicle status. It operates on a 24 V network and communicates with the vehicle networks to exchange status and diagnostics.

Technical features

• Supply voltage: 24 V (truck electrical system).
• Interfaces: sensor inputs (angle/actuator position, speed, status), outputs for solenoid valves and pump of the auxiliary steering electro-hydraulic circuit.
• Communications: vehicle CAN for exchanging status, enable signals and diagnostics with chassis modules (FR/CPC, instrument cluster).
• Control function: reads steering wheel/speed and calculates the setpoint for the steerable axle; manages modes "active", "return to center" and "straight-line lock" at high speeds.
• Hardware: sealed automotive unit with microcontroller, power stage for actuators and fail-safe management (locking/centering in case of fault).

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Functions

• Dynamic control of the steerable rear axle to reduce turning radius and improve low-speed maneuverability.
• Automatic transition to centering/locking of the axle as speed increases to ensure stability.
• Monitoring of sensors (angle, actuator position, circuit pressure) and management of safety strategies with recovery to center in case of fault.
• Diagnostics and fault reporting over the CAN network with error logging and dashboard warnings.

Model applications

• Mercedes-Benz Actros (series equipped with steerable third axle EHZ).

Typical faults

• No diagnostic communication / CAN network fault of the steering module.
• Axle does not steer or remains locked at center, possibly with an auxiliary steering fault message on the dashboard.
• Intermittent steering or slow return due to faults in solenoid valves, power supplies or actuator position sensor.
• Plausibility alarms between steering wheel command and axle position feedback.
• Power supply faults (fuses, connectors, corrosion) causing module shutdown and activation of safe mode (centering/locking).

Final conclusions

The A0004460420 is the key control unit of the E-MAS/EHZ system for managing the steerable third axle on the Actros. It ensures low-speed maneuverability and high-speed stability, with safety strategies focused on centering in case of malfunction

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