Quick answer
Check the colour first. A red light means a serious problem: stop somewhere safe as soon as you can and check your owner’s manual before driving on. An amber or orange light means a fault that needs checking soon, and a flashing light is more urgent than a steady one. Green and blue lights just show that something is switched on.
Is this a DIY job?
- Difficulty: Easy to check and read codes; the repair depends on the fault
- Time: 5 to 15 minutes to check and read codes
- Tools: owner’s manual, OBD2 code reader (optional), torch
- Skills: none for the checks; basic confidence plugging in a code reader
Anyone can do the first checks and read a basic engine fault code. Working out what’s actually wrong, and fixing it, often needs proper diagnostic equipment.
Step by step
- Note exactly what you see. The colour, the symbol, whether it’s steady or flashing, any message on the screen, and whether other lights came on at the same time. Note how the car is driving: any loss of power, noise, smell or steam. A photo of the dash helps the person who diagnoses it.
- If it’s red, stop safely. Pull over when it’s safe, switch on your hazard lights and look up the symbol in the owner’s manual. – Oil pressure light: switch the engine off straight away. Driving on with no oil pressure can wreck the engine quickly. Check the oil level once the car has been off for a few minutes, on level ground. – Engine temperature light: stop and switch off. Don’t open the radiator or coolant cap while the engine is hot: it can spray scalding coolant. – Brake warning light: check the handbrake (or electronic park brake) is fully off. If the light stays on, the brake fluid may be low or there may be a fault in the braking system. Have the brakes checked straight away, even if they feel normal. Don’t drive if the pedal feels soft or goes further than normal. – Battery or charging light: the alternator isn’t charging. The car may run for a while on the battery, but it can stop without much warning. If the temperature is also rising, the belt may have broken: stop. (see How do I know if my alternator needs replacing?)
- If it’s amber, get it checked soon. You can usually drive carefully to a workshop or home, but don’t ignore it. Avoid long trips or towing until it’s been looked at.
- If the engine light is flashing, ease off. A flashing engine or “check engine” light usually means a serious misfire. Unburnt fuel can overheat and damage the catalytic converter. Reduce speed, avoid heavy loads and get it checked promptly. If the car is shaking badly or losing power, stop.
- Check the simple things. Some amber lights have simple causes: a tyre pressure light may just need the tyres pumped up to the placard pressures, and on some cars a loose fuel cap can set an engine fault. Check fluid levels if you know how.
- Read the fault code (optional). Most modern cars have an OBD2 diagnostic port, usually under the dash on the driver’s side. Plug in a code reader with the ignition on and write down every code. Codes starting with “P” relate to the powertrain (engine and transmission).
- Don’t just clear the code. Clearing a code turns the light off but doesn’t fix anything, and it erases information a technician can use. If the fault is still there, the light will come back.
- Book it in. Give the technician your notes, photos and any codes. A code points to the system that has a problem, not always to the exact part, so expect them to test before replacing anything.
Specs table
Common warning lights
Symbols and colours vary between makes. Your owner’s manual has the definitive list for your car.
| Warning light | Usual colour | What it usually means | What to do |
|---|---|---|---|
| Oil pressure (oil can) | Red | Low oil pressure | Stop and switch off now |
| Engine temperature (thermometer) | Red | Engine overheating | Stop, switch off, let it cool |
| Brake system (“BRAKE” or circle with “!”) | Red | Park brake on, low fluid or brake fault | Check park brake; if it stays on, get the brakes checked straight away. Don’t drive if braking feels wrong |
| Battery / charging | Red | Charging system not charging | Head for help; stop if temperature rises |
| Airbag / SRS | Red or amber | Fault in the airbag system | Get it checked; airbags may not work. Professional-only |
| Check engine / engine management | Amber | Engine or emissions fault | Steady: book in soon. Flashing: ease off and get it checked promptly |
| ABS | Amber | Anti-lock braking not working | Normal brakes usually still work; book in soon |
| Tyre pressure (TPMS) | Amber | One or more tyres low | Check and inflate to placard pressures |
| Power steering (steering wheel) | Amber or red | Power steering fault | Steering may be heavy; drive carefully to help |
| Diesel particulate filter (DPF) | Amber | Filter needs to clean itself (regenerate) | Follow the manual; often a longer run at steady speed |
| Glow plug / pre-heat (coil) | Amber | Diesel pre-heat. If it flashes while driving, often an engine fault | Check the manual; book in if it flashes |
Fault code letters
| First letter | System |
|---|---|
| P | Powertrain (engine, transmission) |
| B | Body (airbags, central locking, comfort systems) |
| C | Chassis (ABS, steering, suspension) |
| U | Network (communication between modules) |
Basic code readers usually show P codes only. B, C and U codes often need a more capable scan tool.
What you’ll need
- OBD2 code reader or Bluetooth OBD2 adaptor
- tyre pressure gauge
- If the battery or charging light is on: digital multimeter
When to call an auto electrician
- Any red warning light that stays on after the simple checks.
- The engine light is flashing, or comes back after clearing.
- Airbag/SRS warnings. Airbag systems are professional-only: a fault can stop airbags working, and incorrect handling can set one off.
- ABS, stability control, power steering or electronic park brake warnings.
- Several unrelated lights come on at once. That can point to a charging, earth or network fault.
- Any “hybrid system” or high-voltage warning on a hybrid or EV. Don’t attempt any work on high-voltage parts or orange cables.
Need an auto electrician? Find local auto electricians and mobile services in your city.
Related questions
Q: Can I keep driving with the check engine light on? A: If it’s steady and the car drives normally, you can usually drive carefully until you can get it checked. If it’s flashing, or the car is running badly, slow down and get it seen promptly, or stop if it gets worse.
Q: Will disconnecting the battery reset the warning light? A: Sometimes, but it’s not a fix. The fault is still there, and you lose the stored information a technician uses to diagnose it. It can also reset radio, windows and other settings.
Q: Why did a warning light come on and then go off? A: Some faults are intermittent, and the system turns the light off when the fault stops. The code is often still stored, so it’s worth having it read.
Q: Are cheap OBD2 readers any good? A: A basic reader is useful for reading and recording engine codes. It won’t diagnose the fault for you, and most can’t read airbag, ABS or body codes. (see How do I read fault codes with an OBD2 scanner?)
Q: Why do several warning lights come on at once? A: Several lights together can point to one underlying problem, such as low voltage from a weak battery or charging fault, or a communication fault between modules. Start by checking the battery and charging system.
Sources
- RACV, “What do the car dashboard symbols and warning lights mean” – colour meanings; red or flashing lights often mean stop; oil pressure and temperature: pull over and switch off; brake light that stays on needs checking immediately; charging light points to the charging system; flashing check engine light needs immediate attention; persistent DPF warnings need servicing. https://www.racv.com.au/royalauto/transport/cars/what-do-the-car-dashboard-symbols-mean-and-warning-lights.html (checked October 2026)
- NRMA, “What do my dashboard warning lights mean” – red and orange lights; don’t just reset the light, have a technician diagnose and clear the code. https://mynrma.com.au/cars-and-driving/car-servicing/resources/what-do-my-dashboard-warning-lights-mean (checked October 2026)
- SAE J2012 – Diagnostic trouble code definitions (P, B, C, U code structure). Referenced as the industry standard; not quoted.