E-MAS module for steering axle management for Actros, Axor, Atego

Typical defects:
No communication in diagnostics/CAN network of the steering module
The axle does not steer or remains locked in the center, with a possible auxiliary steering fault message on the instrument cluster
Intermittent steering or slow return due to solenoid valve faults, power supply issues, or actuator position sensor
Plausibility alarms between steering wheel command and axle position feedback
Power supply failures

The component code 350384 is an electronic control unit dedicated to managing the auxiliary steering on Mercedes commercial vehicles equipped with a steerable third axle. It is commonly referred to in the aftermarket as the EHZ/E-MAS module (Elektronik – Elektronische Hinterachs-Zusatzlenkung / Electronically Controlled Multi Axle Steering) and is integrated into the electrohydraulic 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 vehicle networks to exchange status and diagnostic information.

Technical specifications

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

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Functionality

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

Model applications

• Mercedes-Benz Actros/Atego/Axor/Econic (when equipped with EHZ steerable rear axle).

Typical faults

• No communication in diagnostics/CAN fault of the steering module.
• The axle does not steer or remains locked at center, possibly with an auxiliary steering fault message on the dash.
• Intermittent steering or slow return due to faulty solenoid valves, power supplies or actuator position sensor.
• Plausibility alarms between steering input and axle position feedback.
• Power supply faults.

Final conclusions

The 350384 is the key control unit of the E-MAS/EHZ system for managing the steerable third axle on Actros/Atego/Axor/Econic. It ensures low-speed maneuverability and high-speed stability, with safety strategies designed to center the axle in case of a malfunction.

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