What to do if a warning light comes on in a rental car

Modern vehicles can warn drivers about technical problems, low fluid levels, tyre pressure, overheating, engine faults and many other conditions. They do this using dashboard symbols. Some are immediately understandable, while others look as if they were designed for an entrance exam at an engineering university.

If the Check Engine light or another warning indicator appears in a rental car, the main thing is not to ignore it and not to try to “repair” the vehicle yourself automatically.

First assess how the vehicle is behaving, the colour of the warning, any additional symptoms and safely contact the rental company.

Why can dashboard warning lights appear?

A warning light does not always mean that the vehicle has suffered a serious breakdown.

Possible causes include:

• low pressure in one of the tyres;
• low fuel level;
• scheduled maintenance being due;
• low AdBlue level;
• a sensor fault;
• a temporary voltage drop;
• an engine problem;
• overheating;
• low oil pressure;
• a braking system fault;
• a battery or alternator problem;
• an ABS or ESP fault;
• a transmission problem;
• another technical malfunction.

Some warnings may allow you to continue cautiously to a safe location, while others require you to stop as soon as it is safe to do so.

This is why “the light is on, but the car is still moving” is not a complete diagnosis. A vehicle can continue moving while also quite clearly asking you to stop the experiment.

Main rule: do not ignore a warning

If a new symbol or text message appears on the dashboard, pay attention to it immediately.

It is particularly important not to continue driving without assessing the situation if:

• the vehicle loses power;
• the engine runs unevenly;
• there is strong vibration;
• you hear an unusual metallic noise;
• smoke appears;
• you notice a burning smell;
• the engine temperature rises;
• braking performance becomes worse;
• the vehicle responds poorly to the accelerator;
• several warnings appear at the same time.

In these situations, it is safer to stop at an appropriate location and contact the rental company.

Red and yellow warning lights: what is the difference?

The colour of a warning often helps indicate how urgent the situation may be, but it does not replace the instructions for the specific vehicle.

A yellow or orange warning light usually means that a system requires attention, inspection or diagnosis.

A red warning light more often indicates a more serious or urgent situation.

Red warnings may, for example, relate to:

• oil pressure;
• engine overheating;
• the braking system;
• battery charging;
• seat belts;
• the parking brake;
• other critical systems.

However, the same colour does not mean the same level of danger. A red seat belt warning and a red oil pressure warning obviously require completely different actions.

Vehicle manufacturers could have made every symbol perfectly consistent and obvious. Then people might almost never open the manual, and apparently that would be too convenient.

What should you do immediately after a warning appears?

If a new warning light or message appears:

• stay calm;
• check the colour of the warning;
• read the text message if one is displayed;
• pay attention to how the vehicle is behaving;
• check for smoke, smell or unusual noise;
• if the situation appears serious, stop in a safe place;
• take a photo of the dashboard;
• do not clear the fault yourself;
• contact the rental company;
• follow the instructions you receive.

If the vehicle is on a motorway or another dangerous section of road, personal safety is more important than obtaining the perfect dashboard photo. Stop somewhere safe first.

What does Check Engine mean?

The Check Engine light is one of the best-known and at the same time least specific vehicle warnings.

It normally looks like a small engine symbol and indicates that the vehicle’s electronic control unit has detected a fault or a parameter outside its normal range.

Possible causes vary widely:

• a sensor fault;
• an ignition system problem;
• a fuel system problem;
• an emissions control fault;
• a turbocharger problem;
• an air intake fault;
• other engine management problems.

The exact problem cannot be identified from the symbol alone.

So Check Engine does not automatically mean either “the engine is about to explode” or “ignore it and drive for another month”. Reality, as usual, is less convenient.

Check Engine stays on continuously

If the yellow Check Engine light comes on and remains continuously illuminated while the vehicle:

• runs smoothly;
• has not lost power;
• is not overheating;
• does not make unusual noises;
• does not produce smoke;
• responds normally to the accelerator;

there may be a fault that requires diagnosis but does not necessarily require an immediate emergency stop.

However, with a rental car, you should not independently decide to continue driving for several days with the warning present.

Take a photo of the warning and contact the rental company. The next steps should depend on the specific fault and the condition of the vehicle.

What should you do if Check Engine is flashing?

A flashing Check Engine light usually requires more urgent attention than a continuously illuminated warning.

If Check Engine is flashing, especially if:

• the engine is running unevenly;
• the vehicle is jerking;
• there is significant loss of power;
• you smell fuel;
• smoke appears;
• the vehicle accelerates poorly;

you should stop in a safe location as soon as possible and contact the rental company.

Continuing to drive for a long time with a flashing Check Engine light in the hope that the car will “clear itself out” is not a good idea. An engine is not a breathing exercise.

Check Engine and loss of power

Sometimes, together with the Check Engine warning, the vehicle may enter a protective mode and noticeably lose power.

This may appear as:

• poor acceleration;
• the vehicle not reaching its normal speed;
• difficulty driving uphill;
• limited engine speed;
• weaker accelerator response;
• additional dashboard messages.

This type of mode may be used by the vehicle electronics to protect the engine or other components.

If a rental car loses significant power, do not continue a long journey without contacting the rental company, especially on mountain roads, motorways or in heavy traffic.

TPMS tyre pressure warning

The TPMS warning usually looks like a stylised tyre or horseshoe shape with an exclamation mark.

It may appear because of:

• low pressure in one tyre;
• a puncture;
• a change in outside temperature;
• recent tyre inflation or replacement;
• a faulty sensor;
• the system requiring recalibration.

If the TPMS warning appears, visually inspect the tyres at the first safe opportunity.

If one tyre is clearly deflated, damaged or the vehicle begins pulling to one side, you should not continue driving.

If everything looks normal, the warning should still be reported to the rental company and the tyre pressure checked if necessary.

Can you simply reset TPMS?

It is not recommended to reset a tyre pressure warning before confirming that the pressure is actually correct.

Resetting the system does not inflate the tyre and does not repair a puncture. It only tells the vehicle electronics to treat the current values as the new reference point.

It is a little like switching off an alarm clock instead of getting out of bed. The noise is gone, but the morning problem remains.

Red oil pressure warning

A red oil can symbol may indicate a problem with engine oil pressure.

This is one warning that should not be ignored.

If the red oil warning appears while driving:

• stop in a safe place as soon as possible;
• switch off the engine;
• do not continue driving without instructions;
• contact the rental company;
• explain when the warning appeared;
• report any noise, loss of power or other symptoms.

Do not add a randomly selected engine oil unless this has been agreed with the rental company.

Using the wrong oil or continuing to drive with an actual oil pressure problem can cause serious engine damage.

Engine temperature warning

A high engine temperature warning may appear as a thermometer over waves or as a text message.

If the engine temperature is too high:

• find a safe place to stop;
• switch off the engine;
• do not continue driving;
• do not immediately open a hot cooling system;
• contact the rental company;
• report the warning and any other symptoms.

If steam is coming from under the bonnet, do not immediately open the coolant expansion tank or radiator cap.

The cooling system may be under pressure and hot coolant can cause serious burns.

Battery warning light

A red battery symbol does not necessarily refer only to the battery itself. It often indicates a problem with the vehicle’s charging system.

Possible causes include:

• an alternator fault;
• a drive belt problem;
• a weak battery;
• an electrical system fault;
• another charging system problem.

If the warning remains on after the engine starts, the vehicle may continue running for some time, but the battery may gradually discharge.

Do not continue a long journey without consulting the rental company.

Brake system warning

A red brake system warning requires attention.

First check whether the parking brake is still engaged.

If the parking brake is released but the warning remains, or if:

• the brake pedal feels unusually soft;
• braking performance is worse;
• the car pulls to one side;
• you hear unusual noises;
• other warnings appear;

do not continue driving and contact the rental company.

Brakes belong to the small group of vehicle systems where the philosophy of “let’s see what happens next” works particularly badly.

What does ABS mean?

A yellow ABS warning may indicate a fault in the anti-lock braking system.

The standard braking system may continue to operate, but ABS may not be available.

You should:

• report the warning to the rental company;
• avoid aggressive or sudden driving;
• increase your following distance;
• watch for additional warnings;
• follow further instructions.

If the ABS warning appears together with a red brake system warning or the brakes behave abnormally, the situation requires more urgent attention.

ESP or Traction Control warning

The stability control warning often looks like a car with skid marks behind it.

If it flashes briefly while accelerating or driving on a slippery road, this may simply mean that the system is actively intervening.

If it stays on continuously, the system may be disabled or faulty.

Report the warning to the rental company and drive especially carefully on wet or slippery roads until further instructions are provided.

AdBlue warning

Modern diesel vehicles may display a warning when the AdBlue level becomes low.

The vehicle normally provides advance notice and may show the remaining distance before a refill is required.

The warning should not be ignored for too long. On some vehicles, once AdBlue is completely depleted, the engine may not restart after it is switched off.

If an AdBlue warning appears in a rental car, notify the rental company and ask what to do next.

Do not simply buy the first container you see and pour something into an unfamiliar filler opening because the cap happens to be attractively blue. Colour-based decision-making has already caused enough trouble at petrol stations.

Low fuel warning

A low fuel warning is one of the most straightforward dashboard messages.

Even so, it is better not to drive regularly until the tank is almost completely empty.

After the warning appears:

• check the remaining driving range;
• find a suitable nearby petrol station;
• confirm the correct fuel type;
• do not treat the final displayed kilometres as a guaranteed reserve.

The remaining range is an estimate and can change depending on speed, terrain, air conditioning and driving style.

What does Key Not Detected mean?

The message Key Not Detected means that the vehicle cannot recognise the electronic key.

Possible causes include:

• a weak key battery;
• the key being too far away;
• the key being close to a device causing interference;
• the vehicle having a specific emergency key recognition point;
• a temporary system fault.

If the engine is already running, do not switch it off in a random location if there is a risk that the vehicle may not start again.

Contact the rental company and provide the exact wording of the message.

Transmission warning

A transmission fault message may be accompanied by:

• jerking;
• delayed gear changes;
• inability to select a particular gear;
• limited power;
• limp mode;
• unusual noises.

If the transmission is behaving abnormally, do not continue a long journey or try to “free it up” by repeatedly switching between driving modes.

Stop in a safe place and contact the rental company.

What does Service or Maintenance mean?

Messages such as Service, Maintenance Required or similar may mean that a scheduled maintenance interval has been reached.

This does not necessarily indicate a technical fault.

If the vehicle is operating normally, photograph the message and send it to the rental company.

There is no need to independently change the oil or filters or try to reset the service interval. Renting a car is not supposed to result in an unexpected career as a mechanic.

When can you continue driving?

This depends on the specific warning and how the vehicle is behaving.

Cautious driving to a safe location may be possible if:

• the warning is not critical;
• the vehicle operates normally;
• there is no overheating;
• there is no smoke;
• there is no burning smell;
• there is no strong vibration;
• the brakes work normally;
• the rental company has confirmed what to do next.

With a rental car, it is better not to make technical decisions independently, especially if you are unsure what the warning means.

When should you stop as soon as possible?

Stopping safely is particularly important if:

• the red oil pressure warning is on;
• the engine is overheating;
• a serious brake system warning appears;
• Check Engine is flashing and the vehicle is running abnormally;
• the vehicle suddenly loses significant power;
• smoke or steam comes from under the bonnet;
• there is a strong burning or fuel smell;
• you hear loud mechanical noises;
• the vehicle is difficult to control;
• a tyre is visibly deflated;
• continuing to drive may cause further damage.

Choose the safest possible location to stop and take the surrounding traffic conditions into account.

What should you photograph for support?

A clear photo can help assess the situation more quickly.

Useful photos include:

• a full view of the dashboard;
• a close-up of the warning light;
• the text message on the display;
• the current mileage;
• the engine temperature, if shown;
• the affected tyre if the warning concerns TPMS;
• any visible damage or fluid leak, if it is safe to photograph.

Do not stand in an active traffic lane just to get the perfect photo. Support staff will find a living customer with an average photo considerably more useful.

What information should you send to the rental company?

When contacting support, provide:

• the main driver’s name;
• the booking or agreement number;
• the vehicle model;
• the registration number;
• your current location;
• which warning appeared;
• its colour;
• whether it is continuous or flashing;
• when it first appeared;
• how the vehicle is behaving;
• whether there is loss of power;
• whether there is noise, smell, smoke or vibration;
• whether the vehicle can still be moved safely.

A message saying “car problem” is emotionally understandable but technically contains about as much information as “something happened”. A dashboard photo and a few specific details are far more useful.

Why should you not clear fault codes yourself?

Do not connect an external diagnostic device and delete fault codes without approval from the rental company.

A fault code may contain useful information for diagnosing the problem.

If it is cleared:

• the cause may become more difficult to identify;
• useful diagnostic information may be lost;
• the warning may return shortly afterwards;
• resetting the code does not repair the technical problem.

Deleting a fault code does not fix a car. It simply makes the problem less talkative.

Why should you not visit a random garage without approval?

If the rental car has a technical problem, do not independently take it to the nearest workshop without approval from the rental company.

Unauthorised repairs may:

• breach the rental conditions;
• complicate warranty work;
• make the fault more difficult to assess;
• lead to unexpected costs;
• affect reimbursement of expenses;
• create further technical problems.

Report the problem first and wait for instructions.

What if the warning disappears by itself?

If a warning light appears and later goes out by itself, this does not always mean that the underlying problem has completely disappeared.

Some faults can be intermittent.

If a warning has already appeared:

• remember or photograph it;
• note the conditions under which it appeared;
• inform the rental company;
• watch to see whether it returns;
• pay attention to any change in vehicle behaviour.

This is particularly important if the warning was accompanied by loss of power, vibration, overheating or unusual noise.

What if the warning disappears after restarting the car?

Sometimes a warning disappears after switching the vehicle off and starting it again.

This may be caused by a temporary electronic fault, but it does not guarantee that the vehicle has no underlying problem.

Do not repeatedly restart the engine simply to make the warning disappear.

If the message appeared serious, document it and report it to the rental company.

Does roadside assistance cover these situations?

If a warning is caused by a technical vehicle fault, the next steps may include advice, diagnosis, roadside assistance, towing or other measures depending on the circumstances and rental conditions.

It is important to distinguish between a mechanical problem and an issue caused by the customer’s actions.

Assistance conditions may differ in cases such as:

• a mechanical fault;
• a discharged battery caused by a technical issue;
• a tyre puncture;
• a lost key;
• misfuelling;
• negligent use of the vehicle;
• breach of the rental conditions.

The exact costs and coverage depend on the cause of the problem, the selected package and the rental conditions.

Common mistakes when a warning appears

Some reactions can turn a small issue into a more serious one.

Common mistakes include:

• completely ignoring the warning;
• continuing to drive while the engine is overheating;
• driving with a red oil pressure warning;
• continuing with a visibly deflated tyre;
• clearing fault codes yourself;
• repairing the vehicle independently;
• adding an unknown technical fluid;
• going to a random garage without approval;
• failing to photograph the warning;
• not reporting loss of power;
• waiting until the end of the rental to mention the problem.

If the vehicle has decided to tell you that something is wrong, the least effective response is usually to pretend you have never met.

Frequently asked questions about dashboard warnings

Can I drive with the Check Engine light on?

It depends on the type of fault and how the vehicle behaves. If Check Engine remains continuously illuminated and the vehicle operates normally, the situation may not require an immediate emergency stop, but you should report it to the rental company. If the warning flashes, the vehicle loses power, jerks, smokes or runs abnormally, stop safely and contact the company.

What should I do if the red oil warning appears?

Stop safely, switch off the engine and contact the rental company. Do not continue driving without instructions.

Can I drive with a TPMS warning?

Check the condition of the tyres first. If one tyre is clearly deflated or damaged, do not continue driving. If everything looks normal, report the warning and check the tyre pressure if necessary.

What should I do if the engine overheats?

Stop in a safe location, switch off the engine and do not open the hot cooling system. Contact the rental company.

Can I reset Check Engine myself?

This is not recommended. Clearing the warning does not remove the cause and may delete useful diagnostic information.

Do I need to report a warning if it disappears by itself?

Yes, especially if it was accompanied by loss of power, noise, vibration or other symptoms.

Can I drive to a workshop myself?

Only if this has been agreed with the rental company and the vehicle can be driven safely. Do not independently choose a workshop or authorise repairs.

What should I do if the vehicle loses power?

If the vehicle noticeably loses power, especially together with Check Engine or another warning, avoid continuing a long journey. Stop in a safe place and contact the rental company.

What should SOLO rent a car customers do?

If a SOLO rent a car vehicle displays Check Engine, TPMS, an engine temperature warning, oil warning, brake warning or another new indicator, document the warning and contact support.

When contacting support, it is helpful to send a photo of the dashboard, the vehicle registration number, your current location and a short description of how the vehicle is behaving.

If the car loses power, overheats, produces smoke, brakes poorly, has a visibly deflated tyre or shows a critical red warning, do not continue driving without instructions.

Do not clear fault codes, repair the vehicle yourself or take it to an external workshop without approval.

SOLO rent a car works with customers in Malaga, Malaga Airport, Marbella and Alicante. Regardless of where the problem occurs, the more accurately you describe the warning and the behaviour of the vehicle, the faster the next steps can be determined. A photo of the dashboard is usually more useful than ten messages saying “something is wrong”.

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In short

If a new dashboard warning appears in a rental car, do not ignore it. Check the colour, read any message on the display and pay attention to how the vehicle is behaving.

Yellow warnings often mean that inspection or diagnosis is required. Red warnings may indicate a more serious situation, particularly when they concern oil pressure, engine temperature or the braking system.

If Check Engine is flashing, the vehicle loses power, the engine runs unevenly, smoke, smell, strong vibration or overheating appears, stop in a safe place and contact the rental company.

Take a photo of the dashboard and provide the vehicle number, your location and the symptoms. Do not clear fault codes, carry out repairs yourself or visit a random workshop without approval.

A warning light does not always mean a serious breakdown. But if the vehicle has decided to tell you something is wrong, it is worth reading the message. Even if the symbol looks as if it was designed by someone with a personal grudge against drivers.