A Guide To Warning Lights And What They Mean

We’ve all been there; you put the key in the ignition, twist the car into life and suddenly the tiniest of illuminations catches your eye. Somehow, since you last drove the car, the dreaded mechanical goblins and sprites have done their worst, meddling with any under-bonnet fragility they can get their mischievous mits on.

An unwanted dashboard warning light can be simply a requirement to top up some fluid, a faulty sensor or an engine needing proper TLC. At the other end of the scale, it could be a warning beacon for mechanical sorrow. Before you panic, let’s take a look at the some of the more common offenders that can switch on and what they could mean.

Battery charge warning

In most cars, the battery warning light will flick on as you turn the ignition. There is only a problem if it lingers on or comes on suddenly while driving, meaning there could be an issue with your car’s electrical system. The connection at the terminals could have come loose, the battery itself could be on its way out as it struggles to hold voltage or your alternator could be done for.

As explained here, the alternator keeps the battery charged while on the move. So if it has failed, a car can slowly come to a stop as the electrical system has no juice to feed from. Another issue may not be the alternator but the drive belt connected to it. This is also connected to the water pump and power steering, so if this fails, there may be another couple of warning lights flicking up on the dashboard fairly soon.

Brake system and ABS warnings

Possibly the scariest of warning lights, anything under the blanket of the brake system should be checked thoroughly before proceeding. Brake fluid could be low and just needs a top-up or the brake master cylinder could have failed, leading to a loss of assisted braking. Brake lines may have failed also, but in many cases it’s just because the handbrake has been left slightly on.

In terms of ABS, an error within the coding of the ECU may have occurred, needing a reset using a diagnostic system at a garage. If the ABS light switches on, your braking system will still function as normal but without the anti-locking ability but it’s advised to take the car to get sorted as soon as possible. This light is another that will switch on briefly during ignition, just to remind you that it’s functioning.

Check engine warning

A light that could be simply a faulty sensor or a mechanical travesty, the engine warning light is a common feature on cars that haven’t been serviced for a while. A simple lack of oil can cause this light to switch on. The possible causes could also be a faulty sensor within the engine or a mis-performing spark plug, along with other faults that can be read by the ECU and highlighted via the dashboard or a diagnostic computer system.

If this warning light begins to flash, it’s advisable to pull over and seek assistance immediately. The flashing means that something rather serious has occurred under the bonnet and many ECUs are programmed to cut power to enforce a ‘limp home’ mode to possibly save the engine.

Oil pressure warning

Used primarily to alert of a high or low oil pressure, this warning light can also be used to warn of a high oil temperature. High oil pressure isn’t that big of a problem - it’s low oil pressure that needs your utmost attention. A lack of oil flow around the moving parts of the engine can lead to serious heat build up resulting in potentially terminal damage to the powertrain. A decrease in lubrication will see friction increase within the engine block, leading to warping of gaskets, pistons and cylinders.

If this light flicks on, it’s advised to check your engine oil level and top it up if required. If the system is brimmed and still the light stays on, there could be a problem with the oil pump which may need attention or replacing. A flush of the oil lines may also fix an oil pressure issue, relieving the system of any blockages.

Coolant warning

A coolant warning light highlights two things - water temperature and level. Considering the amount of cycles coolant undergoes around the engine block, through coolant pipes and the radiator, the heat transfer will inevitably lead to some coolant changing state into a vapour form, reducing the coolant level slowly over time. This light is here to tell you when the coolant level dips below the minimum point in the reservoir, warning you that before long there may not be enough coolant to keep the heat transfer balanced from the engine.

The serious side of this warning light comes when it means water temperature is too high. This could also be due to a lack of coolant or it could mean a full-out head gasket failure. The radiator may have become blocked from fouling or even broken internally by a stray stone smashing through it while driving. In any case, if the temperature gauge has risen into the red, it’s advised to pull over, stop the car and assess the condition of the engine. It may just need a top-up (water will do to get you home) or the engine could be on its way to welding itself solid from overheating.

Does your car have any constant warning lights? Has a warning light ever saved your car in the knick of time? Comment below with your experiences of these annoying yet helpful alerts.