Symptom
Tyre pressure warning light illuminated
The tyre pressure warning is lit — usually a horseshoe shape with an exclamation mark. A steady lamp normally means a tyre is genuinely low; a lamp that flashes at startup and then stays on usually means the monitoring system itself has a fault rather than a soft tyre. Either way the answer starts the same: check all four pressures with a gauge when the tyres are cold, against the figures on the sticker in the door frame or filler flap.
Also described as: tpms light, tyre light, tire pressure light, tyre pressure warning, flat tyre warning, horseshoe light, tire pressure warning light illuminated, tire light, tire pressure warning, flat tire warning, چراغ باد لاستیک, باد لاستیک کم, چراغ فشار باد لاستیک, luz presion neumaticos, luz presion llantas, testigo presion neumaticos, luz tpms, لمبة ضغط الإطارات, علامة هواء الكفرات, إشارة ضغط الكفرات
What this usually means
Steady and flashing mean different things here, and the difference decides whether you are looking at a tyre or at the system. A steady lamp normally means a tyre is genuinely low. A lamp that flashes for a period at start-up and then stays on is the standard way these systems report a fault in themselves — most often a sensor that has stopped transmitting.
Either way the answer starts the same: check all four pressures with a gauge, cold, against the figures on the sticker in the door frame or filler flap. A warm tyre reads several tenths of a bar higher than the same tyre cold, so a pressure set after a drive is set wrong.
Which system the car has changes what a warning can tell you. A direct system has a sensor inside each wheel and can name the corner and the pressure. An indirect system has no sensors at all — it infers a soft tyre from the anti-lock system's wheel speeds, because an under-inflated tyre has a smaller rolling circumference and turns faster. That means it cannot say which tyre, it cannot see all four going down together, and it must be reset after any pressure adjustment, because the reset is what teaches it the new normal.
Sensor batteries are the failure nobody plans for. They last roughly five to ten years, they are not replaceable, and when one dies the sensor simply stops transmitting — so a car of that age with a lamp that will not clear after correct inflation is usually a sensor at the end of its life rather than a leak.
And a seasonal warning is often not a fault at all. Pressure falls with temperature, so the first cold snap of autumn lights this lamp on cars whose tyres were set in summer.
Working through it
| What you find | Likely cause | How to confirm it | What fixes it |
|---|---|---|---|
| Steady lamp, one tyre measurably low | A genuinely soft tyre — a slow puncture, a leaking valve, or simply time | Gauge all four cold against the door sticker. Inspect the low one for a nail and check the valve with soapy water. | Repair or replace the tyre, then reset the system where it requires one. |
| Flashes at start-up for a period, then stays on | A system fault rather than a soft tyre — most often a sensor that has stopped transmitting | This flash-then-solid pattern is the standard fault indication. Read TPMS codes; a sensor with no signal names itself. | Renew the failed sensor and relearn it to the vehicle. Batteries are not serviceable, so the sensor is the part. |
| Car is five to ten years old, pressures correct, lamp will not clear | Sensor battery at end of life — it has simply stopped transmitting | Read each sensor's signal; the silent one is the answer. Consider the age of all four, since they were fitted together. | Renew the sensor. Fitting one at a time on a car of that age usually means returning for the others. |
| Lamp will not clear after inflating, on a car with no wheel sensors | An indirect system that has not been reset — the reset is what teaches it the corrected pressures | Establish which system the car has. No sensors in the wheels means the reset is mandatory rather than optional. | Run the reset from the instrument cluster menu or button with the tyres correctly inflated and cold. |
| Lamp appeared with the first cold weather, pressures slightly low all round | Normal thermal effect — pressure falls with temperature | Check all four cold. Uniformly low by a small margin across all four is seasonal rather than a leak. | Inflate to the placard figure and reset. No fault. |
| Lamp after a tyre change or a wheel swap | Sensors not relearned, damaged during fitting, or a spare or winter set the car has never seen | Check whether the relearn was performed, and whether the fitted wheels carry sensors at all. | Perform the relearn — automatic, stationary or by diagnostic tool depending on the vehicle. Renew any sensor damaged on fitting. |
-
Steady lamp, one tyre measurably low
- Likely cause
- A genuinely soft tyre — a slow puncture, a leaking valve, or simply time
- How to confirm it
- Gauge all four cold against the door sticker. Inspect the low one for a nail and check the valve with soapy water.
- What fixes it
- Repair or replace the tyre, then reset the system where it requires one.
-
Flashes at start-up for a period, then stays on
- Likely cause
- A system fault rather than a soft tyre — most often a sensor that has stopped transmitting
- How to confirm it
- This flash-then-solid pattern is the standard fault indication. Read TPMS codes; a sensor with no signal names itself.
- What fixes it
- Renew the failed sensor and relearn it to the vehicle. Batteries are not serviceable, so the sensor is the part.
-
Car is five to ten years old, pressures correct, lamp will not clear
- Likely cause
- Sensor battery at end of life — it has simply stopped transmitting
- How to confirm it
- Read each sensor's signal; the silent one is the answer. Consider the age of all four, since they were fitted together.
- What fixes it
- Renew the sensor. Fitting one at a time on a car of that age usually means returning for the others.
-
Lamp will not clear after inflating, on a car with no wheel sensors
- Likely cause
- An indirect system that has not been reset — the reset is what teaches it the corrected pressures
- How to confirm it
- Establish which system the car has. No sensors in the wheels means the reset is mandatory rather than optional.
- What fixes it
- Run the reset from the instrument cluster menu or button with the tyres correctly inflated and cold.
-
Lamp appeared with the first cold weather, pressures slightly low all round
- Likely cause
- Normal thermal effect — pressure falls with temperature
- How to confirm it
- Check all four cold. Uniformly low by a small margin across all four is seasonal rather than a leak.
- What fixes it
- Inflate to the placard figure and reset. No fault.
-
Lamp after a tyre change or a wheel swap
- Likely cause
- Sensors not relearned, damaged during fitting, or a spare or winter set the car has never seen
- How to confirm it
- Check whether the relearn was performed, and whether the fitted wheels carry sensors at all.
- What fixes it
- Perform the relearn — automatic, stationary or by diagnostic tool depending on the vehicle. Renew any sensor damaged on fitting.
Codes that produce this symptom (25)
Listed with the codes that most typically present this way first — the likeliest place to start.
- C0077 Low Tyre Pressure Typical of this code Moderate
- U0127 Lost Communication With Tyre Pressure Monitor Module Typical of this code Low
- U0330 Software Incompatibility With Tyre Pressure Monitor Module Typical of this code Moderate
- U0430 Invalid Data Received From Tyre Pressure Monitor Module Typical of this code Moderate
- C0030 Left Front Tone Wheel Moderate
- C0031 Left Front Wheel Speed Sensor Moderate
- C0032 Left Front Wheel Speed Sensor Supply Moderate
- C0033 Right Front Tone Wheel Moderate
- C0034 Right Front Wheel Speed Sensor Moderate
- C0035 Right Front Wheel Speed Sensor Supply Moderate
- C0036 Left Rear Tone Wheel Moderate
- C0037 Left Rear Wheel Speed Sensor Moderate
- C0038 Left Rear Wheel Speed Sensor Supply Moderate
- C0039 Right Rear Tone Wheel Moderate
- C003A Right Rear Wheel Speed Sensor Moderate
- C003B Right Rear Wheel Speed Sensor Supply Moderate
- C003C Rear Tone Wheel Moderate
- C003D Rear Wheel Speed Sensor Moderate
- C003E Rear Wheel Speed Sensor Supply Moderate
- C006B Stability System Active Too Long Moderate
- C0078 Tyre Diameter Moderate
- U0185 Lost Communication With Antenna Control Module Moderate
- U0258 Lost Communication With Radio Transceiver Low
- U0486 Invalid Data Received From Antenna Control Module Moderate
- U0559 Invalid Data Received From Radio Transceiver Low
Information, not instruction
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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.
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