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The 5 Most Common Causes Of A Check Engine Light

If a check engine light has illuminated on your dashboard, the chances are it's one of these five things causing it

Remind me later
The 5 Most Common Causes Of A Check Engine Light - DIY

Nothing strikes fear into the heart of a conscientious car owner like a check engine light. But, while there is a chance there could be a major issue, it’s highly likely that the problem behind the warning light is something fairly minor.

These are the most common causes of the dreaded CEL:

Faulty oxygen sensor

The 5 Most Common Causes Of A Check Engine Light - DIY

Perhaps the most common cause of all. An oxygen sensor or 02 sensor’s job is to measure levels of oxygen in the exhaust, feeding back information to the ECU. The ECU will then fiddle with the fuel/air mixture as necessary.

If the sensor isn’t working, expect your car to run much richer, burning more fuel. This will eventually cause problems for other components like the spark plugs.

Spark plug or coil issues

The 5 Most Common Causes Of A Check Engine Light - DIY

Speaking of spark plugs, they too can throw up a check engine light. Faulty spark plugs can cause misfires or even cylinders to stop running entirely. The coil packs that sit on top of the plugs can cause the same symptoms when faulty.

Mass airflow sensor fault

The 5 Most Common Causes Of A Check Engine Light - DIY

Remember when we talked about the fuel/air mixture earlier? The MAF or mass airflow sensor plays a crucial role in this process, measuring how much air is going into the engine. If there’s an issue with it, your engine may begin to run more roughly than before, and - you guessed it - there’ll be a check engine light lit up on your dashboard.

Catalytic converter problems

Image via Wikimedia Commons/The RedBurn
Image via Wikimedia Commons/The RedBurn

The honeycomb structure within a catalytic converter - which traps all sorts of nasty pollutants and prevents them from being spat out of the tailpipe - can become clogged or even disintegrate over time. If there’s a problem with your cat, you can expect reduced performance and a sulfur smell emanating from the exhaust.

Loose petrol cap

The 5 Most Common Causes Of A Check Engine Light - DIY

Probably the easiest check engine light to fix. Yes, forgetting to put your fuel filler cap back on can indeed trigger a CEL, as the car recognises the incorrect pressure within the tank.

What to do when you get a check engine light

The 5 Most Common Causes Of A Check Engine Light - DIY

Unless the cause is something blindly obvious like the stray fuel cap mentioned in the previous point, it’s vital that you find the cause of a check engine light as soon as possible. Thankfully with FIXD, it’s really easy. Simply plug our module into your car’s OBDII port, connect to it via Bluetooth, open the FIXD app, and any fault codes will be clearly displayed.

Not only that, but FIXD will tell you the potential consequences of continued driving, give an estimated repair cost, and in some cases even provide a link to a YouTube video for further investigation.

Sound good? Use the discount code ‘CARTHROTTLE’ and get 10 per cent off your FIXD sensor here.

The 5 Most Common Causes Of A Check Engine Light - DIY