The trouble codes are a series of letters and numbers that can help you identify and pinpoint the source of the error message.
Each code begins with a letter. These letters help you identify which system the error is coming from. The meanings of these letters are below:
P: The letter P stands for “Powertrain” and covers the fuel system, engine, transmission, ignition, etc. This contains the largest set of codes.
B: B stands for the “Body” which relates to the seatbelts, airbags, power seating
C: C means “Chassis” and covers everything related to the chassis including the brake fluid, axle, ABS etcetera.
U: U means undefined. These relate to the other aspects of the vehicle.
The letters are followed by a series of 4 numbers. The first number is either 1 or 0. The 0 codes refer to a generic code while the 1 code refers to manufacturer specific code.
The second number refers to the specific subsystem. For example, 7 might mean transmission. Here’s what the other ones mean:
0: Fuel and air metering and auxiliary emission controls
1: Fuel and air metering
2: Fuel and air metering (injector circuit)
3: Ignition system or misfire
4: Auxiliary emissions controls
5: Vehicle speed controls and idle control system
6: Computer output circuit
The third and the fourth number refer to the kind of specific problem the code relates to.
The P means the problem is from the powertrain section.
The 0 represents a generic code shared by all manufacturers.
The 3 represents the subsystem is the Ignition System.
The 01 represents that the cylinder number 1 has a misfire condition.
This could either mean that the dedicated ignition coil has worn out or the cylinder has suffered a leak.
However, these codes do not tell about the actual problem. Instead, they are like symptoms of these problems. For instance, a wiped out alternator will set off a number of 5 codes in other systems with no problem. It is up to you to make the connections and diagnose the root cause.
How to Use an OBD2 Scanner