Is it safe to drive with the ABS light on?

The car still stops. The hydraulic braking system is entirely separate from the anti-lock electronics, so normal braking is unaffected and you will notice no difference in ordinary driving. What you have lost is the anti-lock function during an emergency stop, which is what stops the wheels locking and lets you steer while braking hard. On a dry road at low speed that rarely matters; in the wet, at night, or in traffic it very much can. Treat it as a repair to make this week rather than this month.

Will a wheel speed sensor fault fail an MOT?

Yes. A brake system warning device indicating a malfunction is a major defect, with 85,196 recorded failures in the DVSA data behind this site. The tester checks that the ABS lamp illuminates when the ignition is switched on and then goes out — a lamp that stays on is a failure, and so is one that never comes on at all, because that suggests the warning has been disabled. If the same fault has knocked out stability control, that lamp is a separate major defect with 35,322 recorded failures.

Why is my speedometer not working with C0035?

Because on most cars built in the last twenty years there is no separate speedometer sensor. Road speed is calculated by the ABS module from the wheel speed sensors and broadcast over the vehicle network to the instrument cluster, the engine control unit and the gearbox. Lose a wheel speed sensor and the ABS module may stop publishing a trustworthy speed, so the speedometer, the cruise control and the gearbox strategy all suffer at once. A non-working speedometer is also a defect in its own right at MOT time.

Can I just clean a wheel speed sensor instead of replacing it?

Frequently, yes, and it is always worth trying first. The two most common causes are debris bridging the gap between the sensor tip and the toothed ring, and rust building up inside the mounting bore, which pushes the sensor away from the ring and widens the air gap beyond what it can read. Removing the sensor, cleaning the tip and scraping the corrosion out of the hole costs nothing but time and fixes a good proportion of these. If the ring itself is damaged or the sensor has failed internally, cleaning will not help.

Chassis code · standard

C0035Front left wheel speed sensor not reading

Standard definition: Left Front Wheel Speed Sensor Circuit Malfunction

Last updated 27 July 2026

Quick answer

The ABS module has lost a usable signal from the wheel speed sensor at the front left corner. Your ordinary brakes still work exactly as before, but the anti-lock system, and usually stability and traction control with it, have switched themselves off.

How the car works this out

Each wheel has a sensor reading a toothed or magnetic ring that turns with the hub, and the ABS module watches all four continuously. It checks two things: that the circuit is electrically healthy, and that each wheel's speed is plausible against the other three. A wheel reporting zero while the others show forty is not believable, and neither is a signal that disappears and returns. C0035 is set when the front left corner fails one of those checks. Because anti-lock braking works by comparing wheels against each other, the module cannot operate safely with one missing, so it shuts the system down and lights the lamp rather than guessing.

What you might notice

ABS warning lamp on, usually with the stability control lamp as well
Speedometer reading zero or behaving erratically on some cars
Cruise control refusing to engage
A firm brake pedal with no pulsing under heavy braking, because the anti-lock function is disabled
Hill-hold assist and automatic parking brake release not working
On some cars, the engine management lamp too, because the road speed signal has been lost

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.

1A chafed or fractured sensor wire where the loom flexes with the steering and suspension near the strutCommon
How to check: Turn the steering lock to lock with the wheel off and watch the loom move. Front sensor cables flex every time you steer as well as every time the suspension moves, which is why they fail far more often than rear ones. Flexing the cable by hand while a scan tool shows the live signal will often reveal the break.
2A corroded connector, typically the one tucked inside the wheel arch or behind the linerCommon
How to check: Unplug and look for green deposits and water. UK winters and salted roads are hard on these plugs.
3Rust, brake dust or debris built up between the sensor tip and the reluctor ringCommon
How to check: Remove the sensor and clean both the tip and its bore. A rust scab in the mounting hole pushes the sensor away from the ring and widens the air gap, which is a very common and very cheap fix.
4A damaged reluctor or tone ring, with teeth broken, or rust lifting the ring away from the hubPossible
How to check: Inspect the ring all the way round by turning the hub slowly. A single damaged section produces a signal that drops out at one point in each revolution.
5A failed sensorPossible
6Excessive wheel bearing play, letting the air gap vary as the hub movesPossible
How to check: Rock the wheel at twelve and six o'clock with the car raised. Play here is both a cause of this code and a separate MOT defect in its own right.
7A fault inside the ABS module itselfLess common

What to do about it

1Have all four wheel speeds compared on live data during a slow drive. This is the single most useful test, it takes minutes, and it confirms which corner is genuinely at fault rather than which corner the code names.
2Clean the sensor and its mounting bore before buying anything. Corrosion in the hole is one of the commonest causes and one of the cheapest to put right.
3Check the wiring carefully at the front, because the loom moves with both the steering and the suspension there and fatigue breaks inside intact-looking insulation are common.
4Check the wheel bearing while the wheel is off. Bearing play causes this code and fails the MOT separately, so finding it now saves a second visit.
5Do not put off the repair because the brakes still feel normal. What you have lost is the anti-lock function under emergency braking, and you find out it is missing at the worst possible moment.

Can you keep driving?

Briefly, gently

The ordinary hydraulic brakes are unaffected and the car stops as it always did in normal driving. What has gone is the anti-lock system, and usually stability and traction control with it, so an emergency stop can lock the wheels and you lose the ability to steer while braking. That matters most in the wet, in the dark and on greasy roads. Drive with more space than usual and get it fixed promptly.

Will it fail an MOT?

This is a straightforward major defect. A brake system warning device indicating a malfunction is a major defect, and 85,196 failures have been recorded against it in the DVSA data behind this site. Worth knowing when you read a certificate: DVSA uses the same wording for the anti-lock braking system and the electronic braking system, so the paperwork often does not tell you which one the tester was looking at. If the fault has also disabled stability control, the ESC lamp is a separate major defect with 35,322 recorded failures, and if the wheel bearing turns out to be worn, that is a third defect on the same corner.

The light this turns on

ABS warning lightThe anti-lock braking system has found a fault and switched itself off. Your brakes still work exactly as they always did in normal driving — what you have lost is the system that stops the wheels locking and the steering going light under a hard, emergency stop.

Common questions

Is it safe to drive with the ABS light on?: The car still stops. The hydraulic braking system is entirely separate from the anti-lock electronics, so normal braking is unaffected and you will notice no difference in ordinary driving. What you have lost is the anti-lock function during an emergency stop, which is what stops the wheels locking and lets you steer while braking hard. On a dry road at low speed that rarely matters; in the wet, at night, or in traffic it very much can. Treat it as a repair to make this week rather than this month.
Will a wheel speed sensor fault fail an MOT?: Yes. A brake system warning device indicating a malfunction is a major defect, with 85,196 recorded failures in the DVSA data behind this site. The tester checks that the ABS lamp illuminates when the ignition is switched on and then goes out — a lamp that stays on is a failure, and so is one that never comes on at all, because that suggests the warning has been disabled. If the same fault has knocked out stability control, that lamp is a separate major defect with 35,322 recorded failures.
Why is my speedometer not working with C0035?: Because on most cars built in the last twenty years there is no separate speedometer sensor. Road speed is calculated by the ABS module from the wheel speed sensors and broadcast over the vehicle network to the instrument cluster, the engine control unit and the gearbox. Lose a wheel speed sensor and the ABS module may stop publishing a trustworthy speed, so the speedometer, the cruise control and the gearbox strategy all suffer at once. A non-working speedometer is also a defect in its own right at MOT time.
Can I just clean a wheel speed sensor instead of replacing it?: Frequently, yes, and it is always worth trying first. The two most common causes are debris bridging the gap between the sensor tip and the toothed ring, and rust building up inside the mounting bore, which pushes the sensor away from the ring and widens the air gap beyond what it can read. Removing the sensor, cleaning the tip and scraping the corrosion out of the hole costs nothing but time and fixes a good proportion of these. If the ring itself is damaged or the sensor has failed internally, cleaning will not help.

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