Engine MIL light on? Here’s how to diagnose it yourself.

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The days of going down to the garage for a tune-up is no longer necessary as sophisticated digital systems now self-corrects the fuel mixture and ignition timing at every crankshaft revolution. It really is a perfect system that can keep a car running for years without a mechanic.

That is until you have the red icon of death appear on your dashboard and need to get it fixed. If anything is wrong in the engine room, the Check Engine light will notify you but not really tell you what is wrong, this is also called the MIL, or malfunction indicator lamp.

As we begin to spend more time at home during the virus, you have the oppourtunity to learn more things about your car, and even possibly fix issues yourself.
OBD Error lights

What does the MIL light mean?

When this light is on, it means the PCM, powertrain or other control module is receiving some data that the system cannot recognize; and the system doesn’t know what to do.  Without the information, the computer then guesses what should be a good number to substitute for the sensor’s output and this allows your car to function almost the same. It also illuminates the dashboard light, so the user knows something is not alright, this light can prevent you from passing inspections and can also be dangerous.

How can I remove turn off the MIL?

The car computer stores the so-called fault code, so with the right tools, you or your mechanic can access the system and have some insight into the problem. Once you know the fault, you can repair or replace the parts causing the problem and turn off the dashboard light. You are maybe able to fix it yourself if it not a severe fault and save some bucks by not needing to go to the mechanic. OBD is the connection to your car diagnostic system that is detailed below.

What Is OBD?

OBD means onboard diagnostics, it is a sophisticated digital computer with sensors in your car that is always checking and adjusting as you drive and this keeps your vehicle running in the most efficient and safest way. If there are any problems, the system generates a fault code and will pinpoint the system needing an inspection. Through the years OBD systems have become more sophisticated and now new cars can monitor brakes, airbags and now can even sense tire pressure. OBDII is the latest standard that incorporates access to all onboard systems in your car.

Does my car have OBDII?

Chances are if it is built after 1996 then yes. The term OBDII refers to the connector/interface. A good way to explain is with USB, it is a universal PC connector; before USB there were serial ports of different sizes and shapes, your printer needed one type your mouse needed another. USB changed all this mess and opened the PC to one connector for all devices. In a way,  OBD is the USB of cars, it’s a standard protocol that allows all cars to talk the same language with a universal connection so one tool can access all cars regardless of make. Before OBD scan tools used were expensive and dedicated to a particular brand or manufacturer  With the introduction of more economical and user-friendly scan devices, it is now practical and effortless for almost any car owner to access these OBD-II signals and use them with ease for their own repairs and testing.

Var obd access port
OBDII access port under is the dashboard of most vehicles.

Note: Some luxury cars such as BMW have their own unique connection, but they are rare. (you can easily get an adapter for most unique vehicles).

Where do I buy an OBD tool?

Online or in auto stores, prices may vary from 10 bucks to hundreds for a full-featured device with a computer interface, multiple languages and lots of options and features. A basic OBDII scan tool can diagnose and fix basic fault codes and is excellent for the majority of basic problems, the top end scanners that can get into the more advanced onboard systems such as the security key system and airbags but are pricey. If you don’t want to buy one, you can always borrow a scanner from the automotive store for an hour or two (usually the garage will charge for this, and it might just be cheaper for them to check it out). We also sell a range of OBD code readers that are simple and easy to use.

OBD Scan Basics

If you have grabbed one of the modern scan tools they are usually Bluetooth or USB operated and can operate via a PC, android or apple app, follow the setup instructions to ensure the app and reader are correctly connected. To get started, you’ll need to

  • Plug the scan tool into the OBD II connector under the dash, have a look above where your feet pedals are for the connection.
  • Turn the key on, but don’t start the car engine.
  • Some scan tools or software might ask for several things, including the VIN, model and the engine type. Just follow the instructions given on the screen.
  • Next, you will be looking for an option to check for trouble codes. Some newer (and more expensive) scan tools give you a text explanation. Others may give you a brochure or CD with code explanations. The best way though is to Google for a trouble-code list for your car – there you may be able to find information that might be more useful than just a mere code explanation.
  • Write these codes down before resetting the MIL indicator. Some bargain models don’t let you clear the codes and turn off the MIL light. The basic scanners vary greatly in their complexity and are sure you are ordering the one based on your skill level. A simple code reader is enough to catch the most simple problems related to your car and can fix the basic stuff. A top end scan tool is in the hundreds but will allow you to access more advanced systems and fix complicated problems.
OBD scan torque
A fault code scan on an Android phone using a Bluetooth scan tool and the app “Torque.”

I hope this covers the basics of OBDII and how to decode your car, we also have a more e in depth article about fault codes. If you have any questions like me a comment and grab some of our OBD diagnostics gear now and become a car doctor today!