Symptom
Brake lights stay on when the pedal is released
The brake lights stay lit with your foot off the pedal — often noticed by somebody behind, or found because the battery is flat in the morning. The switch is a cheap plastic part on the pedal box and it fails more often than almost anything else on the car, usually because a rubber stop behind the pedal crumbles and lets the pedal rest a few millimetres further out. The knock-on effects are the tell: cruise control refuses to set, stop-start stops working, and an automatic may not release from park — because every one of those asks the same switch whether you are braking.
Also described as: brake lights wont turn off, brake lights always on, brake light stuck on, rear lights stay on, battery flat brake lights on, چراغ ترمز خاموش نمیشود, چراغ ترمز روشن میماند, luces freno siempre encendidas, luz freno no se apaga, luces freno quedan encendidas, أنوار الفرامل تبقى مضيئة, لمبة الستوب لا تطفي, إشارة الفرامل دائما شغالة
What this usually means
The brake lights stay lit with your foot off the pedal — often noticed by somebody behind, or found because the battery is flat in the morning.
The switch is a cheap plastic part on the pedal box and it fails more often than almost anything else on the car, usually because a rubber stop behind the pedal crumbles and lets the pedal rest a few millimetres further out. The switch's plunger then never returns far enough to open its contacts, so the lamps stay on with nothing electrically broken at all — and the crumbled remains of that stop are often lying in the driver's footwell.
The knock-on effects are the tell: cruise control refuses to set, stop-start stops working, and an automatic may not release from Park — because every one of those asks the same switch whether you are braking. A car with three unrelated-looking complaints and lit brake lights has one very cheap fault.
The battery consequence is the expensive part. Brake lights on a parked car draw enough to flatten a healthy battery overnight, and the fault is usually discovered as a no-start rather than as a lighting problem — so a car that goes flat after standing, whose brake lights are lit, does not need a battery.
A switch that has failed closed internally does the same thing and is separable by disconnecting it: lights that go out with the switch unplugged mean the switch; lights that stay on mean the wiring or the module.
Working through it
| What you find | Likely cause | How to confirm it | What fixes it |
|---|---|---|---|
| Brake lights lit with the pedal released | The switch, most often because the rubber pedal stop has perished away | Look behind the pedal for the stop and in the footwell for its remains. This is the commonest single cause. | Fit a new stop and adjust or renew the switch. One of the cheapest repairs on the car. |
| Battery flat after standing overnight | The lit lamps draining it — the fault discovered as a no-start rather than a lighting problem | Check whether the brake lights are on with the car locked and the pedal released. | Repair the switch. The car does not need a battery for this. |
| Cruise control will not set and stop-start has stopped working | The same switch — every one of those asks it whether you are braking | Three symptoms with one very cheap cause. Read the switch's live state. | Renew and adjust the switch; all three resolve together. |
| Lights go out when the switch is unplugged | The switch itself has failed closed | This is the decisive test and takes a moment. | Renew the switch. |
| Lights stay on with the switch unplugged | The wiring or the module driving the lamps rather than the switch | The same test, opposite result — which moves the fault downstream. | Repair the wiring or the module. |
| Automatic will not leave Park | The shift interlock never sees the brake released and then applied — the same switch again | See the will-not-shift-out-of-park entry, which approaches this from the other symptom. | Renew the switch. Use the manual shift-lock release to move the car meanwhile. |
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Brake lights lit with the pedal released
- Likely cause
- The switch, most often because the rubber pedal stop has perished away
- How to confirm it
- Look behind the pedal for the stop and in the footwell for its remains. This is the commonest single cause.
- What fixes it
- Fit a new stop and adjust or renew the switch. One of the cheapest repairs on the car.
-
Battery flat after standing overnight
- Likely cause
- The lit lamps draining it — the fault discovered as a no-start rather than a lighting problem
- How to confirm it
- Check whether the brake lights are on with the car locked and the pedal released.
- What fixes it
- Repair the switch. The car does not need a battery for this.
-
Cruise control will not set and stop-start has stopped working
- Likely cause
- The same switch — every one of those asks it whether you are braking
- How to confirm it
- Three symptoms with one very cheap cause. Read the switch's live state.
- What fixes it
- Renew and adjust the switch; all three resolve together.
-
Lights go out when the switch is unplugged
- Likely cause
- The switch itself has failed closed
- How to confirm it
- This is the decisive test and takes a moment.
- What fixes it
- Renew the switch.
-
Lights stay on with the switch unplugged
- Likely cause
- The wiring or the module driving the lamps rather than the switch
- How to confirm it
- The same test, opposite result — which moves the fault downstream.
- What fixes it
- Repair the wiring or the module.
-
Automatic will not leave Park
- Likely cause
- The shift interlock never sees the brake released and then applied — the same switch again
- How to confirm it
- See the will-not-shift-out-of-park entry, which approaches this from the other symptom.
- What fixes it
- Renew the switch. Use the manual shift-lock release to move the car meanwhile.
Codes that produce this symptom (10)
Listed with the codes that most typically present this way first — the likeliest place to start.
- C0023 Stop Lamp Control Typical of this code Moderate
- C0040 Brake Pedal Switch A Typical of this code Moderate
- C0041 Brake Pedal Switch B Typical of this code Moderate
- P0504 Brake Switch A/B Correlation Typical of this code Moderate
- P0571 Cruise Control Brake Switch A Circuit Typical of this code Moderate
- P0572 Cruise Control Brake Switch A Circuit Low Typical of this code Moderate
- P0573 Cruise Control Brake Switch A Circuit High Typical of this code Moderate
- P0703 Brake Switch B Circuit Typical of this code Moderate
- P0719 Brake Switch B Circuit Low Typical of this code Moderate
- P0724 Brake Switch B Circuit High Typical of this code Moderate
Information, not instruction
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