Car Warning Lights Explained: What Each Colour Means

A warning light popping up on your dashboard can be unsettling, especially if you're not sure what it means or how urgent it is. The good news is that most warning lights follow a consistent colour system, and once you know what to look for, they're a lot less mysterious.

We run diagnostics on-site at our workshop in Hamilton and can check warning lights for any make or model. Here's a plain-English guide to what the most common lights mean.

The Short Answer

Warning lights follow a colour system. Red generally means stop and get it checked as soon as it's safe. Amber or yellow generally means get it looked at soon, but it's often okay to keep driving in the meantime. Green or blue lights are just information, not warnings. If you're not sure what a specific light means, searching the light's description along with your car's make and model is a quick way to find out, or bring it in for a diagnostic check.

Understanding the Colour System

Red Warning Lights

• Indicate a serious issue that needs immediate attention
• Safest approach is to stop as soon as it's safe to do so
• Examples include the oil pressure and brake warning lights

Amber or Yellow Lights

• Indicate something worth checking soon
• Often safe to keep driving in the short term
• Examples include the check engine and tyre pressure lights

Common Warning Lights Explained

Check Engine

Can mean anything from a loose fuel cap to an engine issue. A diagnostic scan identifies the cause.

Oil Pressure

Usually means low oil pressure. Stop safely and get it checked before continuing to drive.

Battery

Often caused by the battery not being fully charged, rather than a fault with the charging system itself.

ABS or Brake

Relates to the braking or anti-lock braking system. Worth getting checked promptly.

This isn't a complete list. If a light comes on that you don't recognise, searching its description along with your car's make and model is a good starting point, or bring it in and we'll run a diagnostic check.

The Most Common Cause We See: A Low Battery

Here's something worth knowing before you assume the worst: a large share of the warning lights we clear turn out to be caused by a battery that isn't fully charged, rather than an actual fault elsewhere in the car. A low battery can trigger warning lights that look serious but aren't pointing to a real problem at all.

Keeping your battery fully charged, especially if your car sits unused for long stretches or does mostly short trips, solves the large majority of the warning lights we see come through the workshop. If a light comes on after your car has been sitting for a while, a charge is often worth trying before anything else.

What to Do When a Warning Light Comes On

• Search the light's description along with your car's make and model to get a general idea of what it means
• Note when it appeared, such as after starting the car or while driving, which can help with diagnosis
• Consider whether your battery might be low, especially if the car has been sitting unused, since this is the most common cause we see
• Don't ignore it, even if the car seems to be driving fine, since some issues aren't obvious from behind the wheel
• Book a diagnostic check if you're not sure what's causing it or how urgent it is

Warning Lights and Your WOF

Some warning lights relate to safety systems that are also checked during a WOF, so an unresolved light can sometimes cause a fail. Getting a light checked as soon as it appears, rather than waiting until your WOF is due, is the easiest way to avoid a surprise.

Diagnostics, Servicing and Repairs in Hamilton

We run diagnostics on-site at our workshop and can take care of the fix, for any make or model. Visit us 7 days a week at 20 Arthur Porter Drive, Hamilton, or call (07) 849 0083 to book.

Warning Light FAQs

• Can I keep driving if a warning light comes on?
  It depends on the light. Red warning lights usually mean stop as soon as it's safe to do so. Amber or yellow lights usually mean get it checked soon, but it's often safe to keep driving in the short term. If you're not sure what a specific light means, search the light's description along with your car's make and model, or book a diagnostic check.
• Why did my check engine light come on?
  It can be triggered by all sorts of things, from a loose fuel cap to a more significant engine issue. A diagnostic scan is the best way to find out exactly what's triggering it.
• What does the oil light mean?
  It usually means your engine oil pressure is low, which can be serious. If this light comes on while driving, it's best to stop safely and get it checked before continuing.
• What does the battery light mean?
  It usually points to an issue with the charging system, such as the alternator, rather than the battery itself. It's worth getting checked soon, since your car can lose power unexpectedly if it's not addressed.
• Why do so many warning lights turn out to be nothing serious?
  A low battery is one of the most common causes. When the battery isn't fully charged, it can trigger warning lights that don't reflect an actual fault elsewhere in the car. Keeping your battery fully charged solves the large majority of the warning lights we see.
• Can warning lights affect my WOF?
  Yes, some can. A warning light that indicates a safety-related fault can cause a WOF check to fail, so it's worth getting any light checked before your next WOF is due.
• Can 4Guys diagnose a warning light for me?
  Yes. We run diagnostics on-site and can let you know exactly what's triggering a warning light and what it needs.

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