Automobile fault codes are alphanumeric codes that identify a particular problem in a car. They are generated by the car's on-board diagnostics (OBD) system when it detects a malfunction. The OBD system is a computer-based system that monitors and controls various aspects of the car's performance, including the engine, transmission, emissions system, and other components.
When the OBD system detects a problem, it stores a fault code in its memory. The fault code can then be retrieved using a scan tool, which is a device that plugs into the car's OBD port. The scan tool will display the fault code, as well as a description of the problem.
Fault codes are classified into two main categories: generic and manufacturer-specific. Generic fault codes are the same for all cars, regardless of make or model. Manufacturer-specific fault codes are unique to a particular make or model of car.
The first character of a fault code indicates the category to which it belongs:
- P - Powertrain (engine and transmission)
- B - Body
- C - Chassis
- U - Network and wiring
The second character of a fault code indicates whether it is a generic or manufacturer-specific code:
- 0 - Generic
- 1 - Manufacturer-specific
The last three characters of a fault code provide more specific information about the problem. For example, the fault code P0101 indicates a problem with the mass air flow (MAF) sensor.
Here are some examples of common fault codes and their descriptions:
- P0101 - Mass air flow (MAF) sensor circuit range/performance problem
- P0171 - System too lean (bank 1)
- P0300 - Random/multiple misfire detected
- P0420 - Catalyst system efficiency below threshold (bank 1)
- P0500 - Vehicle speed sensor circuit malfunction
If the check engine light comes on in your car, it is important to have the fault codes read by a qualified mechanic. The mechanic will be able to diagnose the problem and recommend the necessary repairs.