OBD codes can confuse pretty much everyone...even mechanics. The thing that most "Uncle Ed's" don't know about is that just because you have a code for a certain part on the car does not mean that that part needs to be replaced. It means that that SYSTEM is having a problem and it needs further diagnose to determine why the computer is setting the code.
This problem is made worse by auto parts stores that are trying to sell auto parts. Some of them (definitely not all) will try to get you to buy the part that they think is the problem simply by reading the code. That being said I actually advise you to go to your local auto parts store to get the codes read unless you have a great local mechanic that you know and trust. Auto parts stores will usually read them for free. The key is to not let the guy at the store talk you into buying any parts. His job is to sell you a part, not figure out what is wrong with your car.
After you know the code you can come back to this site and look up the meaning as well as common causes and diagnostic aids. On the next few pages of this section you will find an article that I've written about the most common obd codes and the things that commonly cause the problem.
Let's take a look at what obd codes actually are.
Most codes that you will see are "generic", usually starting with P0xxx, but there are also codes called "manufacturer codes". These are sometimes more specific, but information about them is hard to find. If you are looking for manufacturer specific codes I recommend you use an online repair manual.. There you will be able to find much more information about it to help you figure out the cause. I have reviewed the best ones here.
This information should work for any vehicle built from 1996 to current (there are always exceptions though).
Example P0340 (Camshaft sensor code)
1st digit: B is for Body, C is for Chassis, P is for Powertrain, U is for Network
2nd digit: 0 is for SAE aka generic, 1 is for mfg (Manufacturer Specific Codes)
* 1 Fuel and Air Metering
* 2 Fuel and Air Metering Injector Circuit
* 3 Ignition System (Including Misfires)
* 4 Auxiliary Emissions Controls
* 5 Vehicle Speed Controls And Idle Control System
* 6 Computer Output Circuit
* 7 Transmission
* 8 Transmission
4th & 5th digit - two place fault code 0-99
Types of DTC’s
There are two types of obd codes (DTC's) that apply to OBD II. I have them listed below with Type 1 being the more important because they can cause quick and severe damage. Type 2 being not quite as important but you still need to deal with it.
OBD Codes are grouped into these categories
Now you have a better idea of what makes up a dtc (diagnostic trouble code). You can see that every digit has it's purpose. You also know which system is having the problem just by knowing what the first few numbers are. Let's take a look at some specific codes and find out what the likely fixes are.
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