Understanding Warning Light Colours
Dashboard warning lights follow a traffic-light system:
| Colour | Meaning |
|---|---|
| Red | Urgent — stop as soon as it is safe; continued driving risks serious damage or danger |
| Amber/Yellow | Warning — investigate and book a service promptly; can usually drive short distances |
| Green/Blue | Information only — a system is active (e.g., high beam, turn signal) |
Never ignore a red warning light. Never habitually ignore an amber one.
The Most Common Warning Lights Explained
Check Engine Light (Engine Management Light)
Symbol: An engine outline (sometimes with a lightning bolt inside) Colour: Amber
The check engine light is triggered by the ECU (engine control unit) detecting a fault in the engine management system — anything from a loose petrol cap to a failed oxygen sensor, catalytic converter, or misfire.
- Steady light: A non-urgent fault. Book a diagnostic scan within a few days
- Flashing light: An active misfire is occurring; unburned fuel is entering the exhaust and can destroy the catalytic converter. Reduce speed, avoid heavy acceleration, and book immediately
A check engine light is an automatic WoF failure.
Battery Warning Light
Symbol: A battery with + and − terminals Colour: Red
Illuminates when the electrical charging system is not functioning correctly — usually because the alternator has failed or the drive belt has snapped.
Action: The car is running on battery power only. Turn off non-essential electrics (air con, heated rear window). Drive directly to the nearest workshop or home. Do not turn the engine off — you may not be able to restart. Expect 15–30 minutes of running time depending on how charged the battery is.
Oil Pressure Warning Light
Symbol: An old-fashioned oil can with a drop Colour: Red
This is one of the most serious dashboard lights. It means oil pressure has dropped below the safe threshold — not necessarily that the oil level is low. Possible causes: low oil level, oil pump failure, blocked oil pickup, oil leak.
Action: Pull over safely and stop the engine immediately. Do not drive further. Check the oil level. If the level is fine and the light returns immediately on restart, do not drive — call roadside assistance. Driving with low oil pressure can destroy an engine in minutes.
Engine Temperature Warning Light
Symbol: A thermometer in water (wavy lines) Colour: Red (or amber for "approaching high")
Means the engine coolant is overheating. Possible causes: low coolant level, failed thermostat, blocked radiator, failed water pump, blown head gasket.
Action: Pull over safely, turn off the engine. Do not open the radiator cap — coolant is under pressure and boiling hot. Call a mechanic. Driving an overheating engine can result in a blown head gasket or warped cylinder head — repairs costing $2,000–$6,000+.
ABS Warning Light
Symbol: "ABS" in a circle, or "ABS" alone Colour: Amber
The Anti-lock Braking System has detected a fault (usually a wheel speed sensor). Your standard brakes still work, but ABS will not activate during emergency braking — wheels can lock up.
Action: Book a diagnosis within a few days. Avoid driving in conditions requiring emergency braking (heavy rain, icy roads) until repaired. This is a WoF failure.
See: ABS System Explained
Airbag / SRS Warning Light
Symbol: Person with airbag deploying in front of them Colour: Red or amber
The airbag and supplemental restraint system (SRS) has a fault. The airbag may not deploy in a crash.
Action: Book a diagnosis promptly. Do not drive long distances until repaired. This is a WoF failure.
See: How Airbags Work
TPMS (Tyre Pressure) Warning Light
Symbol: Cross-section of a tyre with "!" inside Colour: Amber
One or more tyres is significantly underinflated (typically 25% below recommended pressure).
Action: Stop when safe and check all four tyre pressures with a gauge. Inflate to the correct pressure (found on the door jamb sticker). If no tyre is obviously low and the light persists, a TPMS sensor fault needs diagnosis.
See: TPMS Explained
Brake Warning Light
Symbol: "!" in a circle (sometimes inside a circle with ears — the brake disc shape) Colour: Red
Can mean:
- Handbrake is applied — most common (driver has forgotten to release it)
- Brake fluid level is low — check the reservoir under the bonnet; low fluid indicates worn pads or a leak
- Braking system fault — if the handbrake is released and fluid level is fine, a brake system fault needs immediate professional attention
Action: If not the handbrake, stop driving and call a mechanic. Low brake fluid from a leak can result in brake failure.
Power Steering Warning Light
Symbol: Steering wheel with exclamation mark, or "EPS" Colour: Amber or Red
Electric power steering (EPS) has a fault. Steering may become very heavy, requiring significantly more effort.
Action: Drive carefully to a mechanic — steering still works but is difficult without assistance.
Service Indicator Light
Symbol: Spanner/wrench, or oil can, or text such as "SERVICE" Colour: Amber
Reminds you that a scheduled service is due, based on distance or time elapsed. Not an emergency, but do not ignore it — regular servicing prevents minor issues becoming major failures.
Action: Book a service within the next 1,000 km or 1–2 weeks.
Glow Plug Light (Diesel Engines)
Symbol: Coiled spring or spiral symbol Colour: Amber or Red
On diesel vehicles, the glow plug light illuminates briefly at startup while the glow plugs warm the combustion chambers — this is normal. If it stays on after startup or comes on while driving, a glow plug or engine management fault is detected.
Quick Reference: Act Now vs Book Soon
| Light | Act Now | Book Soon |
|---|---|---|
| Oil pressure | Yes — stop immediately | |
| Engine temperature | Yes — stop immediately | |
| Battery | Yes — drive directly to workshop | |
| Check engine (flashing) | Yes — reduce speed, book urgently | |
| Brake warning (fluid low) | Yes — stop, call mechanic | |
| Airbag/SRS | Yes — within days | |
| ABS | Yes — within a week | |
| Check engine (steady) | Yes — within a week | |
| TPMS | Check pressures immediately; repair soon | |
| Service indicator | Yes — within 2 weeks |
WoF and Warning Lights
Any warning light that is illuminated at the time of a WoF inspection and indicates a fault with a safety system will result in a fail. This includes: check engine (steady or flashing), ABS, airbag/SRS, brake warning. Get all warning lights diagnosed and resolved before presenting your car for a WoF.