Fault codes (Trouble Codes):
When vehicle’s computer detects any problems with the engine, transmission, Fuel system, chassis etc, it saves information as a fault code or trouble code. Such fault codes usually turn Check Engine light ON on the dashboard.
OBD-II (On-Board Diagnostic):
All cars from 1996 or later must have OBD2. To check for faults you need to connect to your vehicle’s computer via an OBD2 adapter. There are a number of OBD2 code readers available in the market. Prices and functionality of these devices vary. Some examples are INNOVA, RioRand, Autel etc.
These devices can read, display and reset the fault codes, you’ll need some code reference or service manual to understand what that code means. For example P0302 means that your engine’s second cylinder is misfiring and P0455 means that you’ve probably left your gas cap open. Some advanced units may store the fault codes in the device’s memory that can be retrieved later. You can search Internet databases (Like OBD-codes.com) for trouble code values, possible reasons and fixes.
Using an OBD 2 reader:
I will use ELM 327 in this article which is an inexpensive code reader with Bluetooth connectivity.
To read fault codes you need to attach OBD 2 reader to your vehicle’s computer. This slot is usually under the steering wheel near break paddle. If LED turn ON, the device is connected.
2- Turn Ignition key to ON position
3- If you have an IPhone or Android phone you can download OBD2 reader apps. Some apps are available for free, Carista, ScanMaster and Torque etc. I will explain two of them.
Open carista app and turn Bluetooth ON, select OBD2 and pair devices. Click on CHECK FAULTS while ignition is in ON position.
Let this process complete. If you see NO FAULTS FOUND it means your vehicle’s computer does not have any fault codes stored. To check if your vehicle is ready for emission test click on EMISSION TESTS and see the status.
In case a fault code apears you can read the fault code with a brief description. If your cell phone is connected to the internet you can click on fault code to find further details over the internet. To reset all fault codes click on RESET OBD2, all stored codes will be erased.
In this app you can go to settings and select OBD2 device.
Some screen shots of this app are included here, you can easily go through them and understand.
It can show you emission test readiness, Freez Frame Data etc.
If you have any questions please feel free to leave a comment.