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What does it mean when my engine warning light is on?

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Updated 9 Oct 2019Bruce McMahon
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Cars today have a myriad of warning lights - from low fuel readings to alerting a driver to an errant door ajar.

In some cases, these lights, often with obvious symbols, replace old-fashioned gauges on the instrument panel.

While all should be heeded, some of these are simple cautions, some are a touch more alarming.

And today, alongside the obvious attention needed for low oil levels or engine temperature warnings, there is the ubiquitous engine warning light in yellow, orange or red.

Some makers call it a ‘malfunction indicator lamp’, others refer to it as the ‘check engine light’.

Most use an outline of an engine, a pictogram, to catch your attention; this symbol will normally come on when the ignition is switched on, then - if all is right with the engine and all its elements - disappear from the display when the vehicle starts.

What does a warning light do?

The engine warning light is connected to the modern car’s engine management system, the computerised box of tricks which overlords and controls all aspects of a motor’s workload - from fuel intake to exhaust temperatures.

That Engine Control Unit (ECU) continually monitors a swag of sensors and then masters the mechanics for optimum engine performance under a range of conditions.

So when the ECU detects a problem that it cannot resolve - discovers that something from fuel load to engine timing to exhaust emissions is not at 100 per cent - it triggers that malfunction warning light.

What does the light mean?

The issue could be minor, such as a loose, ill-fitting sensor.

In this case the warning light may come on and remain steady.

The vehicle may lose power but continue to drive.

Or if there is a more serious problem with a major failure somewhere in the system - electronic or mechanical - that engine light should constantly flash out its warning.

Can I keep driving?

If the engine light remains steady and there are no other warning lights - oil pressure, water temperature - plus no dramas with brakes or steering, it’s possible to continue at an easy pace.

Remember engine power could be reduced.

But do not drive on forever, the car should be checked as soon as feasible.

If the warning light is flashing, the matter is likely to require more urgent attention.

Slow right down, avoid heavy acceleration and don’t drive much further before having the car seen to; remember that if proceeding slowly, or pulling to the side of the road, engage the hazard lights and let other drivers know you have an issue.

What next?

In either case - a steady or a flashing engine warning light - a mechanic with the right diagnostic tool can plug into your car’s ECU and the computerised system should advise where the problem is to be found.

The only sure thing about an engine’s ‘malfunction indicator light’ is that you will find the right expert to sort out the problem by accessing the AutoGuru app or website.

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Written ByBruce McMahon

Bruce McMahon is a Queensland-based journalist who’s spent a fair slice of his career dealing with automotive matters.

His first car was a 1949 Riley Roadster, followed by a mix of machinery from Porsches to Jeeps, Alfa Romeos and Range Rovers through to the current four-wheel drive Mazda ute.

He’s driven the Nurburgring and the Tanami Tracks.