This corolla has a p0420 error code.

Check Engine Light – How to Check Error Codes

Is your check engine light on? You don’t have to go to the dealer or to a shop and pay $50 or more to have them figure out what the problem is! Getting an engine scanner is cheap and easy, and one of the best car-maintenance investments I have made!

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Diagnosing Check Engine Light Error Codes

Your vehicle (if it was made after 1996) has a computer on-board that reads the sensors all over the car and keeps track of anomalies. If a sensor reads something that could be a problem, it triggers the “Check Engine Light.” I used to hate this light, but after getting an OBD2 scanner, it is so nice being able to read the engine codes associated with the light. Instead of dreading what the problem could be and taking it to a shop or auto parts store and borrowing their reader, just read the codes yourself! It is a very empowering feeling.

Some of the engine error codes that I have been able to read and diagnose with this device include:

Range of OBD2 Scanners

The price of these scanners can range anywhere from $15 – $100 or more. The less you pay, the fewer bells and whistles. Higher-end units include Bluetooth connectivity to connect to your iPhone or Android device. Here are a couple options, from cheapest to most expensive:

  1. Bare Bones – “Just Works” – Plug it in and read the codes off the screen (no description – you must Google the codes to figure out what the problem is). Not fancy, but gets the job done. Also allows you to reset the Check Engine Light (CEL).
  2. Bluetooth Scanner – Connects to a Phone via Bluetooth and an App (details below). I was not able to figure out how to reset the CEL with this one, though this may be possible now with updated apps.
  3. ANCEL AD410 – Mid-Range – Plug this one in, read the codes from the screen and gives a brief description of the problem. Allows you to reset the CEL.
  4. High-end Bluetooth Scanner – Connects to iPhone or Android. Very portable. Comes with free app that rates highly. Allows you to reset the CEL.

More Details on Each OBD2 Scanner

The following is a brief discussion of each of these units.

The dreaded “Check Engine Light”!


“Bare Bones”

If you like to go old-school, with something that “just works,” I recommend going with a stand-alone engine reader. This simple, robust unit is pretty cheap, I have one of these (but they no longer sell them) and I leave it in the glovebox or center console, and it’s always there ready to go if I need it.

I bought a bare bones unit; nothing fancy, you just plug it into the port under the steering wheel, like so:

It just tells you the codes, then you go to your phone or computer and Google the codes to figure out what they mean. This one run around $25 on Amazon.com.

OBDII Scan Tool

I used this guy just the other day. My check engine light came on while driving on the freeway. At my next stop, I hooked this up in a parking lot and knew what the deal was in less than 5 minutes.


Bluetooth Engine Scanner

The next option is a small OBDII device that plugs into your car. I got one of these, it will set you back about $20. With this unit and accompanying app, I was able to read codes but not reset the Check Engine Light, which I see as a major downside. I could monitor the engine while driving, seeing live updates of flow rates and fuel economy, etc…

The odb2 reader with the switch installed.

OBDII Scan Tool with Bluetooth

Then you connect over Bluetooth to this device through the use of an app on your phone. The most common paid app is called Torque (Torque for Android) (Torque on iOS), it costs around $5. The best free app I found is called Dash (no longer available).

Either of these apps will connect to the OBDII device and give you stats while you drive. They will also tell you your error codes that have ride to your check engine light.


ANCEL AD410

The mid-range unit with a screen is the ANCEL AD410. The advantage of this unit is that it has the code lookup database right on the unit itself. With this one you can also reset the CEL.

ANCEL AD410


BlueDriver

The higher end Bluetooth option is the BlueDriver. This is probably the most convenient of the 4 listed here. It is very small, perfect for the user who will be scanning more than one vehicle because it is so portable. This also comes with a free app. The advantage of this is that the app is constantly being updated, so you can get new features after you already own the unit.

BlueDriver OBD2 Scan Tool

Thanks for reading, and I hope you found this post helpful. Check out these posts for helpful vehicle maintenance tips!

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