The Electronic Power Steering (EPS) control module, also known as the Power Steering Control Module (PSCM) or Steering Control Module, is the component that controls power steering in modern vehicles with electric assist.
In most contemporary cars, steering assist is not governed by the engine or transmission alone. Instead, an electronic control unit dedicated to steering receives inputs from sensors and directs the steering motor to provide the appropriate level of assist. The exact naming varies by manufacturer, but the function remains the same: coordinate inputs such as steering torque, wheel angle, and vehicle speed to determine how much assist to apply.
The EPS control module: the brain of electric power steering
Key data flows and hardware involved in EPS:
- EPS control module (PSCM / EPS ECU)
- Steering torque sensor (measures how hard you’re turning the wheel)
- Steering angle sensor (wheel position)
- Vehicle speed sensor
- Electric motor or actuator that provides assist
- Power supply and voltage regulation
- CAN bus/network connecting to other modules (ECU, ABS/ESC, body control module)
These components work together to adjust assist in real time, often with different modes for comfort, sport, or high-speed stability.
Variations by system type
Some cars use pure EPS, others use electro-hydraulic power steering (EHPS). Each arrangement has a central module, but terminology and architecture differ:
EPS (electric power steering)
In EPS systems, the motor on the steering rack or column provides direct assist. The EPS control module issues commands to the motor and uses sensor inputs to modulate assistance. No hydraulic pump involvement is required for steering assist.
EHPS (electro-hydraulic power steering)
In EHPS, an electric pump drives hydraulic pressure to the existing hydraulic steering system. An ECU (often still called the EPS or PSCM) controls a valve that modulates hydraulic pressure to the steering rack, allowing electronic control of assist without running the pump at full flow all the time.
How it interfaces with other vehicle systems
The EPS module constantly communicates with other controllers over the vehicle’s data network to ensure safe operation, integrating with systems such as:
- Engine control unit (ECU)
- ABS/ESC stability control
- Body control module
- Telemetry or telematics systems in some models
When a fault is detected, the EPS system may default to a reduced-assist mode or disable assist entirely, flagged by a warning light on the dashboard.
Troubleshooting and diagnostics
If steering feels heavy, sticky, or noises are heard, a diagnostic approach typically includes checking:
- EPS warning lights or fault codes via a scan tool
- Sensors: torque sensor, angle sensor, speed sensor
- Electrical connections and fuses
- CAN bus communication integrity
Because EPS relies on sensors and networks, resolution often requires service by a qualified technician who can interpret error codes and perform targeted tests.
Summary
In summary, the power steering in modern vehicles is controlled by the Electronic Power Steering (EPS) control module, commonly called the EPS PSCM or Steering Control Module. It processes data from steering and vehicle sensors and commands the steering motor (or hydraulic valve in EHPS) to deliver the appropriate level of assist, while coordinating with other vehicle systems over the CAN bus.