On-Board Diagnostics (OBD):
On-board diagnostics (OBD) is an automotive term relating a vehicle’s self-diagnostic and reporting capability. OBD systems give the vehicle owner or repair technician access to the status of the assorted vehicle sub-systems. The quantity of diagnostic information available via OBD has varied widely since its introduction within the early 1980s versions of on-board vehicle computers. Early versions of OBD would simply illuminate a malfunction indicator light or “idiot light” if the problem was detected but wouldn’t provide any information on the character of the matter. Modern OBD implementations use a standardized digital communications port to produce real-time data. Additionally to an identical series of diagnostic trouble codes, or DTCs, which permit an individual to rapidly identify and remedy malfunctions within the vehicle.
Kinds of OBD:
There are two varieties of on-board diagnostic systems: OBD-I and OBD-II.
OBD-I refers to the primary generation OBD systems that were developed throughout the 1980s. These early systems use proprietary connectors, hardware interfaces, and protocols. A mechanic who wanted to access diagnostic information typically had to shop for a tool for each different vehicle make. OBD-I scan tools that support multiple protocols are furnished with an array of various adapter cables.
In the early 1990s, the Society of Automotive Engineers (SAE) and International Standardization Organization (ISO) issued a collection of standards that described the interchange of digital information between ECUs and a diagnostic scan tool. All OBD-II compliant vehicles were required to use a typical diagnostic connector (SAE J1962), and communicate via one of the qualities OBD-II communication protocols. OBD-II has first introduced in model year (MY) 1994 vehicles and has become a requirement for all cars and lightweight trucks starting with MY1996.
The European on-board diagnostics (EOBD) regulations are the European equivalent of OBD-II, and apply to all passenger cars of category M1 (with no more than 8 passenger seats and a Gross Vehicle Weight rating of 2500 kg or less) first registered within EU member states since January 1, 2001 for petrol (gasoline) engined cars and since January 1, 2004 for diesel engined cars.
For newly introduced models, the regulation dates applied a year earlier – January 1, 2000 for petrol and January 1, 2003 for diesel.
For passenger cars with a Gross Vehicle Weight rating of greater than 2500 kg and for light commercial vehicles, the regulation dates applied from January 1, 2002 for petrol models, and January 1, 2007 for diesel models.
The technical implementation of EOBD is essentially the same as OBD-II, with the same SAE J1962 diagnostic link connector and signal protocols being used.
With Euro V and Euro VI emission standards, EOBD emission thresholds are lower than previous Euro III and IV.
EOBD fault codes
Each of the EOBD fault codes consists of five characters: a letter, followed by four numbers. The letter refers to the system being interrogated e.g. Pxxxx would refer to the powertrain system. The next character would be a 0 if complies to the EOBD standard. So it should look like P0xxx.
The next character would refer to the sub system.
- P00xx – Fuel and Air Metering and Auxiliary Emission Controls.
- P01xx – Fuel and Air Metering.
- P02xx – Fuel and Air Metering (Injector Circuit).
- P03xx – Ignition System or Misfire.
- P04xx – Auxiliary Emissions Controls.
- P05xx – Vehicle Speed Controls and Idle Control System.
- P06xx – Computer Output Circuit.
- P07xx – Transmission.
- P08xx – Transmission.
The term “EOBD2” is marketing speak used by some vehicle manufacturers to refer to manufacturer-specific features that are not actually part of the OBD or EOBD standard. In this case “E” stands for Enhanced.
When to Replace PCM?
The onboard computer is that the brains of the engine system, so when the brain isn’t functioning correctly neither is that the engine or the rest that the microprocessor controls – which can include the charging system, transmission, various emission controls, and communications with other onboard control modules. Once a diagnosis has been made (and I emphasize the word diagnosis), then and only then should the PCM get replaced.
All too often, the blame falls on what’s least understood. If an engine isn’t running right and also the cause isn’t obvious, blame the pc. Throwing parts at an issue in an effort to resolve it should be good for the parts business, but attempting to return a replacement PCM because it didn’t fix the matter isn’t good for anyone. Warranty returns on complicated and expensive components like powertrain control modules will be tricky and are a situation for everybody.
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