Engine Management Light Diagnosis

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If your engine management light suddenly flashes on, it’s time to head to the garage. This light tells you that there’s something wrong with the car – not necessarily the engine – and that it’s something that needs immediate attention. Your garage or mechanic can use a code reader to “ask” the management system about the problem.

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Frequently Asked Questions

Why would my engine management light suddenly come on?

The engine management system monitors lots of components within your car, such as the catalytic converter, the airflow sensor, your fuel pump, your spark plugs and so on. These are fundamental components and so if they’re not working properly, you need to know ASAP.

How much does an EM repair cost?

Of course, the exact cost depends on which component is faulty and on where you are, but most repairs or replacements come in at between £50 and £100.

Does the EM light affect an MOT?

The light itself won’t fail the MOT for you, but the underlying reason for it activating could well do. You might still be able to drive the car, but it won’t be working at optimum levels and may be pumping out excessively high emissions, for example.

Can I diagnose the problem myself?

With an engine management light warning, you’ll most likely need a mechanic to diagnose the issue with their code checking equipment, so you’re best advised to book into a garage.

My engine management light has come on and I don’t know what’s wrong!

If you don’t know what’s wrong, we can help find a garage near you which can diagnose and fix your engine management light. Simply follow the steps below.


Enter your registration

Vehicle Milage

Select “Engine Management Light Displayed”


Enter your postcode

Phone number

Any additional information


Set-up an account

Sit back & relax

Wait for the quotes to roll in

Start by entering your registration to receive quotes!

Common causes for the EM light to activate

An oxygen sensor needs replacing

Your oxygen sensors send information back to your electronic control unit (ECU) to tell it how much fuel is being burned. They do this by measuring the amount of oxygen in the exhaust gases and if one or more of them (there’s usually two to four) is failing, your EM light will come on.

Usually, the sensors get covered with oil and soot deposits, which impedes their accuracy. This is a relatively easy issue to resolve as long as you don’t leave it too long.

A loose or faulty fuel cap

A loose fuel cap will also set off your EM light as fuel vapour is highly flammable. In addition to this, any leakage will affect your fuel consumption and mileage.

Always make sure that your fuel cap is replaced securely every time you fill up. If your fuel cap is secure but the light is still on, there may be cracks in or around the tank or the cap and if you see any damage, get to a garage as soon as you can.

Your catalytic converter is faulty

Your catalytic converter converts carbon monoxide and dangerous hydrocarbons into carbon dioxide and water. If your “cat” is starting to fail, you’ll have difficulty accelerating and you’ll see your fuel consumption rising. 

Your catalytic converter is most likely to sustain damage if other parts, like your oxygen sensors, are failing. It’s important to replace or repair your catalytic converter if it’s faulty, both for the environment and your own safety.

Your mass airflow sensor

The light in your car will switch on if the mass airflow sensor becomes faulty or breaks, however, it is possible to drive despite the part failing.

If your mass airflow sensor is failing your EM light will come on. You can still drive with this fault, but your sensor filter will need to be replaced once a year or so to make sure it’s working properly.

Failing spark plugs

If your EM light is on and it doesn’t seem to be one of the other problems causing it, then it could be your spark plugs. These components start off the combustion process to get your car moving and so if you’re having difficulty starting or accelerating then they could be the reason.

Like the air sensor filter, spark plugs are easy and cheap for your mechanic to replace.

Driving with the EM light activated

You can drive with your EM light on, but ideally you should be driving to a local garage! The light is flashing for a reason and you need to find out what the reason is and get the appropriate repairs or replacements so that your car is safe to drive.

It’s also possible that the smaller problem which has activated the light will grow or affect other components, leading to larger and more expensive repairs, so you need to ask Mechanics Near You.

Finding a local garage to diagnose your engine management light problem

AutoAdvisor has a huge network of garages and mobile mechanics that we work with. Once you create your account, just enter your car registration number, make and model, your location and a description of your car’s problems. Once all that information is in, our system will deliver a batch of free, no-obligation quotes into your AutoAdvisor portal for you to choose from.

Get Quotes For Engine Management Light Repairs Now!

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