Power Steering Warning Light: MOT Pass or Fail?

The rarest assessed lamp, and the least forgiving fault

Of the warning lamps a tester assesses, this is the one that shows up least often — 206 vehicles in our records, against thousands for the engine management light. That is a function of how the fault behaves, not of how serious it is. Steering assistance does not degrade gently over years the way pads and tyres do; it works, and then a motor, a torque sensor or a control unit fails, and it does not.

Almost every car now uses electronic power steering rather than the older hydraulic pump driven off the engine. An electric motor on the column or the rack adds torque in the direction you are already turning, guided by a torque sensor that measures how hard you are twisting the wheel and a steering angle sensor that knows where the wheel is pointing. It is lighter, it costs no fuel when you are going straight, and it is entirely dependent on electronics staying happy.

What actually goes wrong

• Torque sensor failure. The system no longer knows how hard you are steering, so it withdraws assistance rather than guess. The commonest genuine EPS fault.
• Motor or control unit failure. Often heat- or moisture-related, and on column-mounted systems usually replaced as an assembly.
• Low voltage. Steering assistance draws a large current at full lock. A tired battery, a failing alternator or a corroded earth can drop the supply far enough for the system to shut down protectively — which is why an EPS lamp and a battery lamp appearing together usually point at the charging system, not the steering.
• Calibration lost after work. Steering angle sensors need setting up after a rack, column, wheel alignment or airbag clock spring job. The lamp then reports a fault that is really an uncompleted procedure.
• Water ingress. Rack-mounted motors sit low and take road spray; connectors corrode and the fault becomes intermittent before it becomes permanent.

Why intermittent is worse, not better

An EPS fault that comes and goes is the dangerous version. Full assistance and no assistance are both manageable — you adapt to either within a corner. The transition between them is not, because the effort required at the rim can multiply while you are mid-manoeuvre. If your steering has ever gone heavy unexpectedly, treat that as the symptom that matters, whatever the lamp is doing at the time.

What the tester checks on the steering

The electronic lamp is a small part of a long inspection. The tester turns the wheel with the car on the ramp and watches for play at the column, the rack and every joint; checks the rack gaiters for splits, because a split gaiter lets grit into the rack and destroys it; inspects track rod ends and ball joints for wear; and confirms the steering lock and linkage are secure. Those mechanical items are ordinary MOT failures on older cars and are much more likely to catch you out than the lamp.

A free MOT history check will show whether steering play or a deteriorating rack gaiter has already been recorded as an advisory on this car. Steering advisories are among the most reliable predictors of next year's failure, because the wear that produced them only ever goes one way.

What the MOT record shows

Frequently asked questions

Before you spend anything on diagnostics, check what this car has already been failed for. A free MOT history check returns every failure and advisory on the registration in the tester's own words — including whether this lamp has been recorded before.