Power steering warning light on: causes and what to do

Electric power-assisted steering (EPAS) systems use an electric motor mounted on the steering column or rack to provide assistance. If the motor itself fails, the system loses all electronic assistance and the warning light illuminates. The car remains steerable because the mechanical connection between the steering wheel and the road wheels is intact, but the effort required rises significantly, particularly at low speeds and during parking manoeuvres. EPAS motors can fail due to internal winding faults, brush wear in older designs, or overheating caused by repeated full-lock manoeuvres. The failure is usually permanent rather than intermittent and does not resolve itself.

Typical repair cost: EPAS motor replacement: £400 to £900 including parts and labour on most vehicles. On some cars the motor is integrated with the steering column and the assembly must be replaced as a unit, pushing costs to £600 to £1,400.

Older vehicles and many commercial vehicles still use hydraulic power steering, where a belt-driven pump circulates fluid under pressure through the steering rack to provide assistance. If the fluid level in the reservoir drops, the pump draws air as well as fluid and assistance becomes erratic or disappears entirely. Low fluid is almost always caused by a leak rather than consumption, because hydraulic power steering is a closed system. Common leak points include the high-pressure hose from the pump to the rack, the low-pressure return hose, the rack seals, and the pump shaft seal. Topping up without finding the leak is only a temporary fix and can mask a worsening problem.

Typical repair cost: Power steering fluid top-up: £10 to £20 for fluid. High-pressure hose replacement: £120 to £300. Rack seal replacement or rack exchange: £300 to £700. Pump seal replacement: £150 to £400.

On hydraulic power steering systems, the pump is driven by a belt from the crankshaft and must maintain consistent fluid pressure throughout the steering circuit. Internal wear in the pump, particularly to the vanes or gears inside it, causes pressure output to drop progressively. A pump that has failed completely delivers no assistance at all and the warning light will illuminate alongside very heavy steering. Belt-driven pumps can also seize, which places sudden high load on the drive belt and can cause the belt to snap, potentially disabling other belt-driven components such as the alternator or water pump if they share the same belt.

Typical repair cost: Power steering pump replacement: £250 to £600 including parts and labour. If the drive belt has also been damaged: add £60 to £150. On some vehicles the pump is difficult to access and labour costs are higher.

Modern EPAS systems rely on a steering angle sensor to know the position and rate of movement of the steering wheel so the motor can deliver the right level of assistance at the right moment. If the sensor develops a fault, the EPAS control module cannot operate the assist motor correctly and disables power steering assistance as a safety precaution, triggering the warning light. Steering angle sensors can fail due to internal electronic faults, contamination, or calibration errors that arise after a wheel alignment, tyre change, or battery replacement. On vehicles where the sensor is integral to the clock spring assembly, a clock spring fault may trigger both the power steering warning light and the airbag warning light simultaneously.

Typical repair cost: Steering angle sensor replacement: £120 to £350 including parts, labour, and recalibration. Recalibration alone (if the sensor is undamaged but has lost its calibration): £50 to £100 at a garage with suitable diagnostic equipment.

The steering rack converts rotational movement of the steering wheel into the lateral movement that turns the road wheels. On electric power steering vehicles, the assist motor may be mounted directly on the rack rather than the column. If the rack develops an internal fault, such as worn or damaged rack teeth, leaking seals on a hydraulic rack, or a failed assist motor on an electric rack, the power steering warning light will illuminate. Steering rack wear is more common on higher-mileage vehicles and those that have suffered significant pothole or kerb impacts that transmit shock loads directly through the steering system. A leaking hydraulic rack typically announces itself with a slow deterioration in steering feel before the warning light appears.

Typical repair cost: Steering rack replacement (hydraulic): £400 to £900 including parts and labour. Steering rack replacement (electric): £500 to £1,200. Rack seal replacement (hydraulic): £250 to £500 if the rack internals are undamaged.

The EPAS control module (also called the power steering ECU) processes inputs from the steering angle sensor, vehicle speed sensor, and torque sensor to determine exactly how much assistance the motor should provide at any given moment. If the module develops an internal fault, it typically shuts down the assist system entirely rather than risk providing unpredictable assistance, and illuminates the warning light. Module failures are less common than motor or sensor faults but do occur, particularly on vehicles affected by moisture ingress (modules are sometimes located in exposed positions under the bonnet or beneath the dashboard), or following electrical faults such as a short circuit or an overvoltage event.

Typical repair cost: EPAS control module replacement and programming: £300 to £800 on most vehicles. Some modules can be repaired by specialist electronics firms for £100 to £300, which is worth exploring before buying a new unit. Programming the replacement module to the vehicle is an additional cost if carried out separately.