C0023: Stop Lamp Control
What to do
Get someone to check your brake lights actually come on — a car braking with no brake lights is a serious risk of being hit from behind, and you cannot see them yourself. Check the bulbs first; that is often all it is. On many cars the cruise control and gear selector also stop working, which is the same switch.
What this code means
The stop lamp control circuit has a fault.
The brake lights are on this list because the ABS module now drives them, and because they are a legal requirement rather than a convenience.
A car that brakes without showing a brake light is the classic cause of being hit from behind, and the driver has no way of knowing — you cannot see your own brake lights.
Why the ABS module is involved: the car has to illuminate the brake lights when it brakes itself — emergency braking, adaptive cruise, stability intervention — and the pedal switch cannot report a stop the driver did not ask for. So the module was given control of the lamps. Many vehicles also flash them under heavy braking to warn following traffic.
Check the bulbs and the pedal switch first. A failed bulb, corrosion in a lamp holder, or a brake pedal switch out of adjustment are far commoner than a module fault, and the switch is a frequent failure in its own right.
Ask someone to stand behind the car while you press the pedal. It takes a minute and it answers the question the code cannot.
Likely causes
Start here
- Faulty brake light switch · easy
- Blown brake light bulb or corroded holder · easy
- Corroded or loose connector · specialist
- Damaged wiring harness · specialist
Less common
- Faulty stability control module · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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