In brief, electric power steering stops working primarily due to electrical supply problems, faulty sensors or the steering motor, or electronic control faults that can trigger limp mode. These issues can appear suddenly or develop gradually, often with a warning light signaling the fault.
Common causes of EPS failure
Electrical system faults are the main culprits, but mechanical wear and software issues also contribute. The issue typically falls into a few broad categories.
Electrical supply and wiring
- Low or unstable battery voltage from a weak battery or failing alternator
- Blown fuses or damaged relays powering the EPS system
- Damaged wiring harnesses from wear, moisture, or accidents
Electrical problems often trigger warning lights and can reduce or cut off steering assist entirely.
Motor, sensors, and control hardware
- Faulty EPS motor or winding short that prevents motor rotation
- Torque sensor or steering position sensor failure leading to incorrect assist commands
- Electronic control unit (PSC/ECU) faults or failed calibration
- Communication issues on the vehicle's CAN bus that disrupt EPS data
When sensors or the control unit fail, assist can become inconsistent or unavailable and may require recalibration or replacement.
Software, safety modes, and external factors
- Software glitches or outdated ECU firmware that misreads inputs
- System enters limp mode to protect itself after a fault
- After certain repairs or aftermarket installations, miscalibration can occur
- Water intrusion or impact damage from collisions can affect EPS electronics
In many vehicles, a fault will be accompanied by a warning light and reduced assist to maintain steering control.
Symptoms and safety considerations
Recognizing warning signs early can prevent a sudden loss of steering and improve safety on the road.
- Steering feels heavier than normal, especially at parking or low speeds
- EPS warning light, steering assist fault, or check engine light on the dashboard
- Intermittent or total loss of steering assist while driving
- Unusual noises such as whining, grinding, or clunking when turning
- Inconsistent assist that changes with speed or engine temperature
- Vibration or stiffness in the steering wheel
Drive with caution if any of these signs appear and have the system diagnosed promptly to avoid sudden steering loss.
What to do if EPS stops working
If you experience a failure of electric power steering, take these steps to stay safe and arrange service.
- Steer with extra effort and gradual movements; avoid sudden or aggressive maneuvers
- Safely pull over to the side of the road and turn off the engine, then restart to see if the problem persists
- Check for warning lights and test whether any steering assist remains or if the wheel feels completely heavy
- If the problem persists, do not drive long distances; contact roadside assistance or tow to a qualified shop
- Have a professional perform diagnostic checks, including battery/charging system tests, EPS motor and torque sensor tests, and software calibration
Note: Some vehicles may allow manual steering but require more effort; continued driving with a faulty EPS can pose safety risks and lead to further damage.
Prevention and maintenance tips
Regular maintenance and awareness can reduce the likelihood of EPS failures and help catch issues early.
- Regularly test the 12V battery and charging system; replace aged batteries and keep connections clean and tight
- Inspect wiring harnesses and connectors to the EPS components for signs of wear, corrosion, or water intrusion
- Install any recalls or service bulletins related to EPS and ensure software is up to date
- Avoid aftermarket electrical modifications that could affect the EPS system or its wiring
- Address warning lights promptly and have faults diagnosed by a qualified technician rather than attempting DIY resets
Proactive maintenance and timely repairs help preserve steering feel and safety on the road.
Summary
Electric power steering failures typically arise from electrical supply problems, faulty sensors or motors, and control-module or software faults. A proper diagnosis involves checking the battery and charging system, inspecting wiring and connectors, testing the EPS motor and torque/steering sensors, and applying any necessary software updates or recalibration. When EPS fails, warning indicators and potential limp-mode behavior are common. Prompt professional assessment and repair are essential for safety and reliability.