What does the stability control light actually mean?

It depends on whether it is flashing or steady. A lamp that flashes briefly while you drive is the system working — it is telling you it has just intervened because a wheel lost grip, which is normal on a wet roundabout. A lamp that stays on permanently means the system has a fault and is switched off. Many cars also have a separate switch to turn stability control off deliberately, which usually lights the same or a similar symbol along with a message, and that is not a fault.

Will a stability control fault fail an MOT?

Yes. A stability control lamp indicating a malfunction is a major defect, recorded 35,322 times in the DVSA data behind this site. If the same fault has also lit the ABS lamp, which is common because the two functions usually share a module, that is a separate major defect with 85,196 recorded failures. Both would be listed on the same certificate.

Is U0122 the same as U0121?

Often in practice, though not in principle. U0121 says the ABS module has gone silent; U0122 says the stability control module has. On most cars the stability function is built into the ABS module, so one unit failing produces both codes and there is only one thing to repair. On cars with a separate vehicle dynamics module — typically a small unit low in the centre console housing the yaw rate and lateral acceleration sensors — U0122 can appear on its own, and then it is a genuinely different fault.

Can I drive without stability control?

You can, and every car built before it became common managed without. The honest answer is that the car will behave exactly as normal until the moment it starts to lose grip, which is the moment the system would have acted. Research consistently shows stability control prevents a meaningful number of loss-of-control crashes, so driving without it means leaving more margin, particularly in the wet, on ice and on unfamiliar roads. It is also a major MOT defect, so it is not something to leave indefinitely.

Network code · standard

U0122No communication with the stability control module

Standard definition: Lost Communication with Vehicle Dynamics Control Module

Last updated 27 July 2026

Quick answer

The car has lost contact with the module that runs electronic stability control. On many cars this function lives inside the ABS unit, so this code and U0121 often appear together and mean the same underlying fault.

How the car works this out

Stability control compares where you are steering with what the car is actually doing, using the steering angle sensor, a yaw rate sensor and a lateral acceleration sensor, then brakes individual wheels to correct a slide. The module doing that work publishes its status on the network. U0122 is stored when those messages stop. The first question worth asking is where the function physically lives: on most cars it is integrated into the ABS module, in which case this code travels with U0121, while on others it is a separate dynamics unit, often under the centre console, and can fail on its own.

What you might notice

Stability control and traction control lamps on
ABS lamp on as well where the two functions share a module
No intervention on a slippery road where you would normally feel the system work
Hill start assist and trailer stability assist unavailable
Occasionally a message about the system being unavailable rather than faulty

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.

1The ABS module having failed or lost power, taking the integrated stability function with itCommon
How to check: Check whether U0121 is also stored. If it is, treat this as one fault rather than two.
2A corroded or wet connector at the moduleCommon
3A failed yaw rate or lateral acceleration sensor unit, on cars where those are combined into a separate dynamics modulePossible
How to check: Find out whether the car has a separate dynamics module, often mounted low in the centre console area, which is vulnerable to spilled drinks and water in the footwell.
4Low system voltage from a battery or charging faultPossible
5Network wiring damage or a poor earthPossible
6A calibration or configuration lost after a module replacement or a software updateLess common
How to check: Ask whether the module has been coded and the sensors calibrated. A correctly fitted but uncalibrated dynamics module will not join in properly.

What to do about it

1Establish whether the stability function is inside the ABS module on your car. It changes the whole diagnosis and stops two codes being treated as two faults.
2Have the battery and charging voltage checked, because unstable supply produces communication codes without anything being broken.
3Look for water in the footwell or console area if the car has a separate dynamics module there.
4Check the module connectors for corrosion.
5Have the calibration checked after any repair. Stability control depends on sensors knowing what level and straight ahead mean, and those references have to be set.

Can you keep driving?

Briefly, gently

The car brakes and steers normally and behaves exactly as it always did right up to the point where it starts to slide, which is precisely where stability control would have intervened. On dry roads at moderate speeds you will notice nothing. In the wet, on a greasy roundabout or on a cold morning, you are driving a car without the system that would otherwise catch it. Adjust accordingly and get it fixed.

Will it fail an MOT?

A stability control lamp indicating a malfunction is a major defect, with 35,322 recorded failures in the DVSA data behind this site. Where this code appears alongside U0121, expect the brake system warning device defect too, which carries 85,196 recorded failures — two major defects from one module. As with every warning lamp in the MOT, the check works both ways: the lamp must illuminate when the ignition is switched on and then go out, and a lamp that never comes on at all is treated as a malfunction rather than as evidence that all is well.

The light this turns on

Stability control warning lightElectronic stability control has found a fault and switched itself off. The car drives normally in a straight line, but the system that detects a skid starting and brakes individual wheels to correct it is no longer available.

Common questions

What does the stability control light actually mean?: It depends on whether it is flashing or steady. A lamp that flashes briefly while you drive is the system working — it is telling you it has just intervened because a wheel lost grip, which is normal on a wet roundabout. A lamp that stays on permanently means the system has a fault and is switched off. Many cars also have a separate switch to turn stability control off deliberately, which usually lights the same or a similar symbol along with a message, and that is not a fault.
Will a stability control fault fail an MOT?: Yes. A stability control lamp indicating a malfunction is a major defect, recorded 35,322 times in the DVSA data behind this site. If the same fault has also lit the ABS lamp, which is common because the two functions usually share a module, that is a separate major defect with 85,196 recorded failures. Both would be listed on the same certificate.
Is U0122 the same as U0121?: Often in practice, though not in principle. U0121 says the ABS module has gone silent; U0122 says the stability control module has. On most cars the stability function is built into the ABS module, so one unit failing produces both codes and there is only one thing to repair. On cars with a separate vehicle dynamics module — typically a small unit low in the centre console housing the yaw rate and lateral acceleration sensors — U0122 can appear on its own, and then it is a genuinely different fault.
Can I drive without stability control?: You can, and every car built before it became common managed without. The honest answer is that the car will behave exactly as normal until the moment it starts to lose grip, which is the moment the system would have acted. Research consistently shows stability control prevents a meaningful number of loss-of-control crashes, so driving without it means leaving more margin, particularly in the wet, on ice and on unfamiliar roads. It is also a major MOT defect, so it is not something to leave indefinitely.

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