The EPS light comes on primarily when the electric power steering system detects a fault—often due to electrical issues, sensor or motor failures, or a drop in voltage or loss of communication with the control module.
Electric power steering uses a motor and sensors to assist steering; when something isn’t right, the system can deactivate assist to prevent unsafe handling and light the warning. Here are the main causes and the steps to diagnose and address them.
Common causes
Below are the most frequent triggers that can set the EPS warning light, spanning electrical faults, mechanical issues, and signal problems.
- Low or failing battery voltage or charging system (alternator problems) that reduce EPS power.
- Faulty or failing EPS motor or its wiring harness.
- Torque sensor or steering angle sensor malfunction within the steering column.
- Faulty EPS control module or loss of communication with other vehicle modules (CAN bus).
- Blown fuses or loose/intermittent electrical connections.
- Overheating of the EPS motor or controller, triggering a protective shutoff.
- Mechanical binding or stiffness in the steering linkage that creates abnormal loads the system detects as a fault.
- Recent electrical repairs or aftermarket modifications interfering with EPS sensors or wiring.
Most EPS faults are fixable, but some may require replacing sensors or wiring or reprogramming the controller. If the light persists, consult a qualified technician for diagnosis and safety assessment.
Electrical and battery issues
EPS depends on a stable electrical supply. A weak battery can cause intermittent or permanent loss of assist. The system may store fault codes related to low voltage or power supply failures. If the battery is older than 3–5 years or shows low cranking power, consider replacement or testing. A failing alternator can also cause voltage dips while driving, triggering EPS faults even if the battery is new.
Sensor and control faults
The EPS relies on sensors such as the torque sensor and steering angle sensor to determine how much assist to provide. Any fault in the sensor, wiring, or the EPS control module can trigger a fault code and illuminate the warning. Communications problems on the vehicle's CAN bus can also disable or degrade EPS performance. In some cases, recalibration or software updates are required after sensor replacement.
Diagnostic steps you can take
Before you head to a shop, you can perform a few checks to gather information and rule out simple causes. Always follow vehicle-specific instructions in your owner’s manual and consider safety first.
- Check the battery and charging system: test the battery voltage (should be around 12.6V when off, 13.5–14.8V while running) and look for warning signs of a failing alternator or parasitic drain.
- Scan for fault codes: use an OBD-II scanner or have a shop pull EPS-related codes (they may be listed under P-codes, U-codes, or manufacturer-specific codes).
- Inspect fuses and connectors: verify the EPS fuse is intact and inspect wiring to the steering column, motor, and sensors for corrosion, damage, or loose connections.
- Check for moisture, corrosion, or water intrusion: water ingress can affect sensors and electronic modules, especially in exposed locations.
- Assess steering feel and operation: if you notice stiff steering, reduced assist, or unusual noises, note when it occurs (temperature, speed, load) to help diagnosis.
- Consider service history and recalls: check for service campaigns or TSBs related to EPS in your vehicle’s year, make, and model.
- Seek professional diagnosis if unresolved: EPS failures often require specialized tooling to test the motor, sensors, and control modules.
Drive cautiously if the system remains unreliable; in some vehicles, you can still steer with reduced assist but it may require more effort, especially at low speeds.
When EPS light indicates a safety risk
If the EPS light stays on or you experience sudden loss of steering assist, treat it as a safety issue. Pull over safely, avoid high-speed maneuvers, and arrange service as soon as possible. Some manufacturers allow temporary operation with limited assist, but reliability varies and damage could worsen if ignored.
Summary
EPS warning lights signal a fault in the electric power steering system, most often caused by electrical issues, sensor or motor faults, or voltage/communication problems. A prudent response includes checking the battery and fuses, scanning for fault codes, inspecting wiring, and consulting a qualified technician to restore safe steering assist.