All new cars now come with an OBD (On Board Diagnostics). This is a fault-registering system connected to sensors all over the car, engine, fuel and emissions system. When the check engine light comes on, it can mean a number of things. There are like 4000 OBD codes that can be stored. OBD diagnostic tools can be plugged in to the OBD port which is normally under the dash on the drivers side. These tools can read out the fault code and/or reset the system to contain no codes. Codes are split into two categories-historical/inactive and active. The historical codes are lists of things that have been detected in the past but are no longer an issue, while the active codes are things that are a problem right now. Codes are subdivided into B-codes (body), C-codes (chassis) and the biggest list of all P-codes (power-train).
P0440 OBD code. This is the most common code you’ll find and its the first thing you should check. P0440 is the code for Evaporative Emission Control System Malfunction which covers a multitude of problems. One thing it covers that you can check for yourself is your fuel cap. Most new cars have a pressurized fuel system and vapor recovery loop. If you’ve filled up with fuel and not twisted the fuel cap until it clicks, you’ve not sealed the fuel system. It won’t pressurize and the OBD system will log a P0440 code. In fact, on a lot of cars that code is so common they’ll actually have some way of telling you to check the fuel cap. So if you get a check engine light, check the fuel cap first and see if the light goes off.
Note : Even if the light does go off, the code will likely still be stored in the OBD system and will show up next time it is checked.
If it wasn’t the fuel cap and tightening it didn’t do it, you’ll need to find someone with an OBD diagnostics tool or reader. Some garages will charge you just for plugging in the device and reading the code. If they do, walk away. They’re ripping you off. Is better to find a garage or mechanic that will read the code and actually give you a diagnosis rather than just making you pay to find out a number.
