Common Dashboard Warning Lights Explained
- Common Dashboard Warning Lights Explained
- As a general rule, red dashboard warning lights indicate a fault requiring immediate attention and amber or yellow lights indicate a fault that should be checked soon. And a flashing engine light is more urgent than a steady one.
Dashboard symbols are not standardised as well as you would hope, and manufacturers use the same icon for different things. But the colour convention is close to universal, and it is the most useful thing to know.
Red means stop and investigate. Amber means a fault is logged and should be looked at. Green and blue are information, not warnings.
Red: stop as soon as it is safe
These three are the ones that can destroy an engine in minutes rather than months. If one comes on while you are driving, pull over.
- Oil pressure (an oil can symbol)
- The most serious light on the dash. It means oil is not circulating at pressure, and an engine without oil pressure can seize in under a minute. Stop, switch off, and do not restart to 'get home'.
- Coolant temperature (a thermometer in liquid)
- The engine is overheating. Stop and let it cool before opening anything, the system is pressurised and will scald. Continuing to drive risks warping the cylinder head or destroying the head gasket, which costs vastly more than whatever caused the overheat.
- Brake warning (a circle with brackets, or 'BRAKE')
- Can be as simple as the handbrake being partly on, or as serious as low brake fluid, which means a leak. If the pedal also feels soft or long, treat it as urgent.
The battery light is not about the battery
A red battery symbol is one of the most commonly misread lights on the dash. It does not usually mean the battery is flat. It means the charging system is not charging, and the most frequent cause is the alternator or its drive belt.
The practical consequence: the car is now running on stored battery charge only, and when that runs out it will stop, wherever it happens to be. You have a limited and unpredictable range. Switch off anything you do not need and head somewhere useful rather than continuing your day.
Amber: the engine light, steady versus flashing
The check engine light (an engine outline, sometimes with the word CHECK) means the engine management system has logged a fault. The important distinction is how it behaves.
Steady means a fault is stored and should be read reasonably soon. The car is usually driveable, though it may have reduced performance if it has entered limp mode to protect something.
Flashing typically indicates a misfire severe enough to send unburnt fuel into the exhaust, which destroys the catalytic converter through overheating. This turns an inexpensive repair into an expensive one quickly. If it is flashing, stop driving and call us.
Amber: the safety systems
These do not usually stop you driving, but they do mean a safety system has disabled itself. And two of them are roadworthy items.
- ABS
- Your normal brakes still work, but anti-lock is off, so the wheels can lock under heavy braking. Often a wheel speed sensor. Assessed in a Victorian roadworthy inspection.
- Airbag / SRS
- The airbag system has a fault and may not deploy in a collision. Worth treating as urgent despite being amber, and also a roadworthy item.
- Traction or stability control
- Flashing briefly while driving is normal. It is the system working. Staying on constantly means a fault, frequently the same wheel speed sensor that triggers the ABS light.
- Tyre pressure (TPMS)
- Check pressures with a gauge, including the spare on some systems. If they are correct and the light stays on, a sensor has failed or needs relearning.
- Diesel particulate filter
- On a diesel, the filter needs regenerating and short trips have not let it. Often cleared by a sustained drive at speed, but if it stays on it needs looking at before the filter blocks.
Why the code alone is not the answer
It is tempting to read a code with a cheap scanner, look up the part it names, and replace that part. This works less often than people expect.
A fault code describes a circuit or an out-of-range reading, not a broken component. A code naming the oxygen sensor circuit can be the sensor, its wiring or connector, or something entirely different that puts the reading out of range, a vacuum leak, or an exhaust leak upstream of it. Replacing the sensor fixes the third case not at all.
So proper diagnosis means reading every module rather than just the engine, looking at live data while the fault is happening, checking freeze-frame data for the conditions when it was logged, and then testing the component and its circuit. That is what separates a diagnosis from a guess. And it is why the intermittent faults are the ones most worth bringing in rather than waiting until the light stays on.
Sources
- Roadworthy certificate, Department of Transport and Planning, Victoria
Car Diagnostics in Craigieburn
Freddy's Auto Care carries out computer diagnostic scanning and fault finding on vehicle engine, transmission, ABS and electrical systems at 14 Potter Street, Craigieburn.
14 Potter Street, Craigieburn VIC 3064
