Why does my power steering come back after I restart the car?

Because the module has latched a fault and shut the assistance down as a precaution, and switching the ignition off resets that latch. On the next start the module runs its self-test, passes it for the moment, and restores assistance until the fault occurs again. It is a very characteristic pattern for an internal module problem, and it is worth describing exactly, because it distinguishes a failing module from a broken wire or a dead sensor, which would not recover on a restart.

Can an electric power steering module be repaired?

Often, yes, and it is worth asking. Specialist firms repair these units, dealing with the failed output stages, cracked solder joints and water damage that account for most internal failures. That is generally much cheaper than a new module or a complete column assembly, and it avoids some of the coding a new unit needs. Occasionally the fault is software rather than hardware and a reflash is enough, so ask whether an update exists before agreeing to anything more drastic.

Why does my steering go heavy after parking manoeuvres?

That is usually the overtemperature protection doing its job. Holding full lock or shuffling in and out of a tight space makes the steering motor work very hard, and the module reduces or removes assistance to stop it overheating. On a healthy car this is rare and recovers within a few minutes. If it happens easily and often, or the assistance takes a long time to come back, the module or motor is likely to be deteriorating and it is worth having checked.

Will an intermittent power steering light fail an MOT?

It fails if it is on when the tester looks. An electric power steering lamp indicating a malfunction is a major defect with 205 recorded failures in the DVSA data behind this site. The tester switches on the ignition, watches the lamp illuminate as a bulb check and confirms it goes out. An intermittent fault might not be present at that moment, so the car could pass — but a lamp that never comes on at all also fails, because the tester cannot confirm the warning system works.

Chassis code · standard

C0735The power steering computer has failed inside itself

Standard definition: Electric Power Steering Module Internal Fault

Last updated 27 July 2026

Quick answer

The control module that runs the electric power steering has reported a fault within itself rather than in a sensor or a wire. Assistance is usually withdrawn, and the classic pattern is heavy steering that comes back after a restart.

How the car works this out

The steering module runs continuous self-tests on its own processor, memory, motor drive circuits and internal temperature. It has to, because it is directly driving a motor attached to the steering. C0735 is set when one of those internal checks fails: a watchdog timeout, a memory error, an output stage reporting a fault, or a supply rail out of tolerance inside the unit. Unlike a sensor code, there is nothing external to test, which is what makes this one different — the module has diagnosed itself.

What you might notice

Steering assistance disappearing without warning, then returning after switching off and restarting
Power steering lamp on, sometimes intermittently
Assistance fading after a period of heavy manoeuvring, then recovering after a rest
A whine or buzz from the steering column or rack
Other steering-related functions such as lane keeping or parking assist unavailable

What causes it

Most likely first. A code names the check that failed, not the part that failed it, so more than one of these can produce the same number.

1An internal electronic failure in the module, commonly from heat cycling and vibration over many yearsCommon
2Water ingress into the module or its connectorCommon
How to check: Look for damp carpets, a blocked scuttle drain or a leaking windscreen seal, particularly where the module is mounted on the column inside the car.
3Overheating protection after heavy use, such as prolonged parking manoeuvres or repeated full-lock turnsPossible
How to check: Note whether the assistance fades after sustained manoeuvring and comes back after the car has stood. That is protection working rather than a component that has failed, though a module that overheats easily is often on its way out.
4Low or unstable supply voltage stressing the modulePossible
5Corroded or high-resistance connections on the module's heavy power supply, which the motor draws throughPossible
6Software corruption, occasionally recoverable by reprogrammingLess common
How to check: Ask whether a reflash or software update is available for the unit before replacing it. It is occasionally the answer and costs far less.

What to do about it

1Describe the pattern accurately to the garage. Assistance that disappears and returns after a restart, or that fades after heavy parking and recovers later, points at the module rather than a sensor and is worth saying plainly.
2Have the battery, charging voltage and the module's power and earth connections checked, because low voltage produces module faults that are not the module's fault.
3Check for water ingress, and fix the leak before fitting anything new.
4Ask about software updates and specialist repair before agreeing to a replacement. Steering modules are frequently repairable, and a new one needs coding to the car.
5Do not keep clearing the code to get the assistance back. A module that has failed its own self-test can drop out at any moment, and knowing it will happen is better than being surprised by it.

Can you keep driving?

Only to a garage

You retain full mechanical control — the wheel is still connected to the road wheels — but the assistance can disappear at any moment and without warning, which is a different proposition from it being permanently absent. Steering that suddenly goes heavy mid-manoeuvre is genuinely startling. Take it steadily, keep the journey short, and avoid situations where you might need to turn quickly.

Will it fail an MOT?

An electric power steering warning lamp indicating a malfunction is a major defect, with 205 recorded failures in the DVSA data behind this site. This code carries a particular MOT risk because it is so often intermittent: the tester checks that the lamp lights at ignition-on and then goes out, and a module that only fails after some use may pass that check on the day. Note that the opposite also fails — a lamp that never illuminates at all when the ignition is switched on is treated as a malfunction, because it suggests the warning has been disabled.

The light this turns on

Power steering warning lightThe power steering system has reported a fault and the assistance may be reduced or switched off entirely. You have not lost steering — there is still a mechanical link from the wheel to the road wheels — but the car will feel heavy, and heaviest of all at parking speeds where you need the help most.

Common questions

Why does my power steering come back after I restart the car?: Because the module has latched a fault and shut the assistance down as a precaution, and switching the ignition off resets that latch. On the next start the module runs its self-test, passes it for the moment, and restores assistance until the fault occurs again. It is a very characteristic pattern for an internal module problem, and it is worth describing exactly, because it distinguishes a failing module from a broken wire or a dead sensor, which would not recover on a restart.
Can an electric power steering module be repaired?: Often, yes, and it is worth asking. Specialist firms repair these units, dealing with the failed output stages, cracked solder joints and water damage that account for most internal failures. That is generally much cheaper than a new module or a complete column assembly, and it avoids some of the coding a new unit needs. Occasionally the fault is software rather than hardware and a reflash is enough, so ask whether an update exists before agreeing to anything more drastic.
Why does my steering go heavy after parking manoeuvres?: That is usually the overtemperature protection doing its job. Holding full lock or shuffling in and out of a tight space makes the steering motor work very hard, and the module reduces or removes assistance to stop it overheating. On a healthy car this is rare and recovers within a few minutes. If it happens easily and often, or the assistance takes a long time to come back, the module or motor is likely to be deteriorating and it is worth having checked.
Will an intermittent power steering light fail an MOT?: It fails if it is on when the tester looks. An electric power steering lamp indicating a malfunction is a major defect with 205 recorded failures in the DVSA data behind this site. The tester switches on the ignition, watches the lamp illuminate as a bulb check and confirms it goes out. An intermittent fault might not be present at that moment, so the car could pass — but a lamp that never comes on at all also fails, because the tester cannot confirm the warning system works.

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