On Board Diagnostics: Notes
WARNING: This page is about a different car, the 2005 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.
- The job of diagnostics is to detect faults and store them so that they can later be read off using the diagnostic tool.
- Diagnostic trouble codes are the result of the fact that much of the software in modern control modules is constantly looking for faults. In an engine management system, for example, more than 50 % of the program code nowadays is used entirely for diagnostics.
- ISO/SAE has specified what diagnostic trouble codes should look like, which is a legal requirement in the USA. ISO/SAE determines all codes which have 0 in the second position.
Examples of diagnostic trouble codes:
- P0107 Manifold Absolute Pressure/Barometric Pressure Circuit Low Input
- P0303 Cylinder 3 Misfire Detected
- P0601 Internal Control Module Memory Check Sum Error
- P0705 Transmission Range Sensor Circuit Malfunction (PRNDL Input)
Table, standards for diagnostic trouble codes
The following are monitored:
- Internal control module faults
- Analog inputs
- Digital inputs
- Outputs