You're driving normally, you shut the engine off at a light, you set off again and suddenly the steering wheel feels as heavy as a tractor's. Or a yellow (sometimes red) steering wheel light with an exclamation mark lights up on the dash. That's almost always a story about the electric power steering system, known by the acronym EPS. In this guide we explain how the system works, how to spot a failure and what options you have left if it happens mid-drive.
What EPS is and how it differs from the old hydraulic power steering
EPS stands for Electric Power Steering. Instead of an engine-driven pump, a belt and pressurised hydraulic hoses, the job of making the wheel lighter is done by an electric motor. It's mounted either on the steering column itself (most common on smaller cars) or on the steering rack (on more powerful and heavier vehicles).
The system has three key components. The torque sensor reads how hard and in which direction you're turning the wheel. The control unit (the EPS ECU) processes that signal and factors in vehicle speed from the CAN network. The electric motor then adds exactly as much assistance as you need. That's why the wheel is light when parking but stable and firm on the motorway.
The difference from the old hydraulic system is huge. No power steering fluid leaks, no belt to snap, no engine load from a pump. On the other hand, everything depends on the electronics and the power supply, so failures look completely different from what drivers were used to with older generations of cars.
How to recognise an EPS failure
The clearest sign is a yellow or red steering wheel light on the instrument cluster, usually shaped like a steering wheel with an exclamation mark next to it. It either appears right when you start the car, or comes on during driving. The light means the control unit has detected a fault and, in most cases, switched off the motor assistance for safety reasons.
The second typical symptom is a suddenly heavy wheel. The car still drives normally, but the steering wheel needs noticeably more effort, especially when parking and in low-speed corners. Some drivers describe it as a feeling that the wheel is "pulling" or "stuck".
The third group of signs is intermittent issues. The wheel works normally, then suddenly goes heavy for a few seconds, then comes back. Or the assistance disappears only when the engine is warm, or only after the car has been sitting for a while. This group also includes strange noises - usually a quiet hum or a squeak coming from the direction of the steering column - and a weak self-centring of the wheel after a corner.
The most common causes we see
In the workshop almost every EPS failure falls into one of five groups.
- Torque sensor. The most common culprit. Over time it degrades, sends a wrong signal and the control unit shuts the assistance off immediately. Often shows up after several years of use or after an impact to the front suspension.
- The EPS motor itself. Brushes wear out, a bearing starts to squeak, a winding burns out. On column-mounted units the problem also tends to appear after water has leaked through the wipers into the cabin.
- The EPS control unit. An electronic board with capacitors and a processor. Damp, vibration and age do their work. On some models this is a known weakness of an entire generation of cars.
- A weak battery and a bad earth. EPS pulls a large current the moment you turn the wheel. If the battery is at the end of its life or the body earth has corroded, voltage drops below the threshold and the system shuts down. The driver thinks it's the power steering, but the problem is in the power supply.
- CAN vehicle-speed signal. EPS uses the speed value from the network. If an ABS wheel sensor or the ABS module is feeding bad data, the power steering doesn't know how much assistance to provide and goes into protection mode.
Without proper diagnostics it's very hard to guess where the problem is, because all of these causes light up the same warning lamp.
Can you drive with the steering warning light on
Short answer: you can, but carefully and only as far as the nearest workshop. The car is still steerable, the brakes still work, but the wheel takes far more effort, especially when parking and at low speeds. That's dangerous in city traffic, in roundabouts and when avoiding an obstacle.
There are situations where the risk is higher. If the light comes on and off during driving, the assistance appears and disappears unpredictably, which can surprise you mid-corner. If the light is red (not yellow), the manufacturer is basically telling you to stop right away. Older drivers and drivers with shoulder or back problems will struggle more to control a heavy wheel, especially in a panic.
A practical workshop tip. If the light comes on out on the open road, slow down, drive calmly to the first safe spot and shut the engine off for a minute. Often after a restart the system comes back to life and you have time to bring the car in for diagnostics without a tow truck. If not, get in touch and we arrange a time.
What we do in the workshop when an EPS fault comes in
The first step is always proper diagnostics. A generic OBD reader often doesn't see the EPS system at all, so we use a professional tool that reads the steering control unit, shows active and stored faults, and the torque sensor values in real time. Only then do we know whether it's the sensor, the motor, the ECU or the power supply.
We also check the battery's state under load, the earths on the engine and body, and the voltages at the EPS connector. Many faults end right there, because replacing a battery or cleaning an earth solves the whole problem without touching the power steering itself.
If the hardware really is faulty, the options are repair or replacement. On some models the torque sensor can be replaced on its own, on others the whole assembly has to go. Electronic boards can often be repaired by specialist shops. Second-hand EPS units from another car are a cheaper option, but they carry the risk of the same failure coming back in a few months. We explain all of that honestly before you decide.
The most important step at the end is calibration. After replacement or removal, the torque sensor and the steering-wheel zero position have to be set correctly. Without calibration the car pulls to one side, the warning light stays on or comes back a few days later. This is where the difference between workshops that have invested in equipment and those that just swap a part really shows.
The price depends on the specific fault and the car model - get in touch for an estimate.
How to extend EPS life in everyday driving
A few habits significantly extend the life of the power steering.
- Don't hold the wheel turned all the way to the lock for long. When parking, the moment you feel the end of travel, ease back a couple of millimetres. In that position the electric motor is working at maximum load and heating up.
- Don't turn the wheel while the car is standing still more than you have to. Roll at least a millimetre, then steer. Less load on the motor, the sensor and the front suspension bearings.
- Look after the battery. A weak battery is the silent killer of EPS. If the car struggles to start or the battery is over four years old, check it before the steering warning light catches you out.
- Watch where you park and how you mount kerbs. A hard hit to the front wheel travels through to the rack and the torque sensor. Typically 4-7 years is a realistic sensor life with normal use, but one heavy impact can cut that down to a few months.
- Don't ignore water in the cabin. Blocked drains under the windscreen tend to fill the front passenger footwell with water, and on some models the EPS control unit sits right there. Damp kills electronics quietly and surely.
If your steering warning light is already on or the wheel is behaving strangely, don't put it off. The sooner you come in for diagnostics, the better the chance the repair stays small. Book an appointment and we'll look the car over on the spot.