A warning light on your dashboard can mean anything from a loose fuel cap to an imminent engine failure. Knowing the difference — and knowing what to do in each case — can save you hundreds of dollars in unnecessary repairs or prevent a serious breakdown.
Colour coding: The first thing to check
Modern cars use a consistent colour system for warning lights:
Red: Immediate attention required. Stop the car safely as soon as possible. Do not continue driving.
Yellow/Amber: Caution. The system requires attention but is not necessarily an emergency. Have it checked promptly.
Green: Informational. A system is active (e.g. cruise control engaged).
Blue: Informational. Usually headlights or high beams.
White: Informational or system message.
Critical red warning lights
Engine Temperature Warning (thermometer in liquid)
**What it means:** Engine coolant temperature is dangerously high. The engine is overheating.
**What to do:** Stop driving as soon as safely possible. Turn off the engine. Do not open the coolant cap until the engine has cooled completely (at least 30 minutes). Call for assistance.
Battery Warning Light (battery symbol)
**What it means:** The charging system is not working. The battery is discharging rather than charging while the engine runs.
**What to do:** Drive to the nearest garage or home if close by. Turn off all non-essential electrics (climate control, stereo). The car will eventually stop when the battery is flat — usually within 30–60 minutes of this light appearing.
Brake Warning Light (exclamation mark in circle with lines)
**What it means:** Either the handbrake is on (check this first), brake fluid is low, or a brake system fault has been detected.
**What to do:** If the handbrake is not the cause, do not drive — brakes may not work correctly. Call for recovery.
Yellow/Amber warning lights
Check Engine Light / Engine Management Light (engine outline)
**What it means:** The engine management system has detected a fault. This could be anything from a loose fuel cap to a major sensor failure.
**What to do:** Check the fuel cap first — this triggers the light surprisingly often. If the light is steady (not flashing), the car can usually be driven carefully to a garage for a diagnostic scan. If flashing, reduce speed and seek assistance soon.
Tyre Pressure Warning (flat tyre with exclamation mark)
**What it means:** One or more tyre pressures have dropped significantly below the recommended level.
**What to do:** Check all tyre pressures (and the spare if fitted) at the nearest petrol station. Inspect for visible damage or punctures. A slow puncture is common — tyres lose pressure over time even without damage.
ABS Warning Light (ABS in circle)
**What it means:** The Anti-lock Braking System has a fault. Standard brakes still work, but the anti-lock function that prevents wheel lockup in emergency stops is disabled.
**What to do:** Can drive with caution, but have it diagnosed. ABS failure in an emergency stop situation (particularly on wet roads) increases stopping distance significantly.
Traction Control / ESP Light (car with skid marks)
**What it means:** Either traction control is actively working (light flashing during wheel spin) or the system has a fault (light permanently on).
**What to do:** If flashing, it is working correctly — reduce speed on slippery surfaces. If permanently on, have the system checked.
Service Due / Spanner Symbol
**What it means:** The car is due for a scheduled service based on mileage or time.
**What to do:** Book a service. This is not urgent within a few hundred miles but should not be ignored indefinitely.
Diesel Particulate Filter (DPF) Warning
**What it means:** The DPF is becoming blocked with soot. This occurs mainly in diesel cars driven predominantly short distances.
**What to do:** Take the car for a 20–30 minute motorway drive at 2,500–3,000 RPM. This passive regeneration burns off the soot. If the light remains, active regeneration at a garage may be needed.
AdBlue Warning (diesel cars)
**What it means:** AdBlue (diesel exhaust fluid) is running low.
**What to do:** Top up at any petrol station before the car enters restricted mode. Some cars will not restart without AdBlue above a minimum level.
EV-specific warning lights
High Voltage Battery Warning
**What it means:** A fault in the high-voltage battery system.
**What to do:** Stop driving. High-voltage faults are potentially dangerous and require specialist attention.
Charging System Warning
**What it means:** The charging system has detected a fault. The car may not charge correctly.
**What to do:** Check charging leads and connectors. If the issue persists, seek professional diagnosis.
Frequently Asked Questions
Can I drive with the check engine light on?**
If it is steady and the car drives normally, usually yes — to a garage for diagnosis. If it is flashing, reduce speed and seek attention within the day. If accompanied by any other warning light, stop.
Why do some warning lights come on briefly at startup?**
This is a bulb/system test — every warning light illuminates briefly when the ignition is turned on to confirm the bulbs are working. This is normal.
How do I reset a warning light?**
Fixing the underlying fault usually resets the light after one to three drive cycles. Disconnecting the battery resets lights but does not fix the fault — it will reappear. Diagnostic equipment can clear codes but again, not the fault.
Is it expensive to diagnose a warning light?**
A diagnostic scan typically costs $50–100 at a garage. Many national tyre and service chains offer free scans. The scan reveals fault codes; additional labour is needed to actually fix the issue.
