I wanted to give a very basic overview of OBDII. OBDII is an acronym for On Board Diagnostic (version) 2 Everycar built after 1995 has this system. The Check Engine Light (CEL) or Malfunction Indicator Lamp (MIL)(same thing) only comes on when a value is out of spec. Where I want to go with this is debunk some myths or wives tales.

Codes do not tell you what is wrong. They only tell you that there is a malfunction in that circuit. Now there can be a few things that can cause the CEL to come on. I am going to take a simple one like an 02 sensor. It could be the sensor itself, wireing harness including a fuse, or the computer. All the PCM knows is that its out of spec. So when going to a parts store to get a code read they are not diagnosing the problem. They are only reading the code and giving a sugestion to sell a part.

There are 2 basic types of codes first is what is called Generic. These are the codes that all those basic mini scaners read. All the generic codes are the same for every car. A P0301 is a cylinder misfire for cylinder number 1 on every car manufacturer. Almost all codes that are P0*** are generic. Then you have Manufacuter specific. That will be a P followed by a four diget code starting with the number 1 i.e. P13**. Now these codes may not be the same for all cars. Chevy(GM) may make this mean something with the coil while Ford may may make it mean something with a driver in the computer.

Codes are also broken down into catagories.
P0001-P0099 - Fuel and Air Metering and Auxiliary Emission Controls
DTC Codes - P0100-P0199 - Fuel and Air Metering
DTC Codes - P0200-P0299 - Fuel and Air Metering (Injector Circuit)
DTC Codes - P0300-P0399 - Ignition System or Misfire
DTC Codes - P0400-P0499 - Auxiliary Emissions Controls
DTC Codes - P0500-P0599 - Vehicle Speed Controls and Idle Control System
DTC Codes - P0600-P0699 - Computer Output Circuit
DTC Codes - P0700-P0899 - Transmission
The P1*** codes will have the same brakedown so if you have a P13** it is something to do with Ignition. Now not every car has every code. If you own a v6 it will not have codes for a cylinder number 8 misfire.

Now that we are this far, there are P2000 and P3000 codes that are Generic. Some are for Diesel and others are for exotic cars like the W12 Bugati Veyron.

And last clearing the code will not make the problem go away. Today false codes are not common though ignoring the CEL can produce secondary codes that will not reture once the original problem is fixed.

I just wanted to touch base on this stuff. I am willing to help with diagnosis and code discriptions.