History of OBD-II
How on-board diagnostics went from California's OBD I in 1988 to OBD-II on every 1996 US car, EOBD in Europe, CAN in 2008 and permanent codes from 2010.
OBD-II grew out of California's emission rules. California's Air Resources Board (CARB) required a first, simple version (OBD I) from the 1988 model year. The second generation, OBD-II, became mandatory on all 1996 model year cars and light trucks sold in the US. Europe adopted the same approach as EOBD from 2001 for petrol cars and 2004 for diesels.
Why it was needed
Studies cited by CARB estimate that excess emissions from emission-related malfunctions make up about half of the total emissions from late-model vehicles. The idea of OBD is to have the car notice those faults itself, tell the driver, and record where the fault is so it can be fixed.
Timeline
| Year | What happened |
|---|---|
| 1976 | Bosch's oxygen (lambda) sensor goes into series production, first on Volvo 240/260 cars for the US market. It lets the engine computer hold the mixture where a three-way catalytic converter works best. |
| Late 1970s–1980s | Carmakers add electronic engine controls and their own diagnostic systems. Connectors, codes and terms differ from maker to maker. |
| Mid-1980s | The US EPA and CARB research OBD systems for emission control. |
| 1988 | CARB's OBD I applies from the 1988 model year. It checks some emission parts, mostly for electrical faults. |
| 1990 | The Clean Air Act Amendments direct the EPA to set federal OBD rules. At a minimum, the catalyst and oxygen sensor must be monitored. |
| 1992 | CARB publishes its second-generation rules, called OBD II. |
| 1993 | The EPA publishes its final rule for federal OBD. |
| 1994–1995 | OBD requirements begin for light-duty vehicles. Makers may ask for waivers, and almost all do. A few gasoline vehicles are already built with OBD II. |
| 1996 | Full compliance is required. Every 1996 and newer gasoline car and light truck sold in the US has OBD II. |
| 1997 | Diesel passenger cars and light trucks must comply. |
| 1998 | The EPA harmonizes federal OBD with CARB's OBD II. |
| 2000–2001 | EU Directive 98/69/EC: EOBD on petrol cars up to 2,500 kg, for new models from 1 January 2000 and all new cars from 1 January 2001 (heavier petrol cars a year later). |
| 2001 | The EPA's original deadline for US emission inspection programs to add OBD checks was 1 January 2001. An April 2001 rule moved it to 1 January 2002 and let states with good cause delay up to 12 more months. |
| 2003–2004 | EOBD on diesel cars up to 2,500 kg, for new models from 1 January 2003 and all new cars from 1 January 2004 (heavier diesel cars: new models from 1 January 2005). |
| 2004–2008 | Federal OBD phases in for vehicles between 8,500 and 14,000 pounds gross vehicle weight rating. |
| 2008 | CARB's rule, which nearly all US vehicles are built to, requires CAN (ISO 15765-4) for OBD communication on every 2008 and newer car and light or medium-duty truck (up to 14,000 lb GVWR). The older SAE J1850, ISO 9141-2 and ISO 14230-4 protocols are no longer allowed on new vehicles. |
| 2010–2012 | Permanent fault codes phase in under CARB's rule: 50% of 2010, 75% of 2011 and 100% of 2012 model year vehicles. A scan tool cannot erase them. |
OBD I and OBD-II compared
| OBD I | OBD-II | |
|---|---|---|
| What it detects | Mostly electrical failures of components | Emission system deterioration and malfunction, as well as electrical failures |
| What it monitors | Oxygen sensors, EGR, fuel delivery, the engine computer, others at the maker's choice | Catalyst efficiency, misfire, oxygen sensor response and heater, EGR, fuel system, evaporative system, secondary air, the engine computer and all its electronic inputs and outputs |
| Check engine light | Goes out as soon as the problem does not come back | Goes out after three driving cycles in a row without the problem |
| Connector, codes and terms | Different for each maker | The same for every maker |
The last row is the change most owners notice. Before 1996, reading codes on two different brands could take two different tools and two different code books. With OBD-II, one generic scan tool reads emission codes on any compliant vehicle, and a code such as P0420 means the same thing on all of them.
OBD, OBD II and EOBD: the names
The EPA notes that "OBD" and "OBD II" are used interchangeably today. The split came from timing: CARB's second-generation rules were called OBD II, while the EPA's first federal rules were simply called "federal OBD". As the two sets of rules were harmonized, the names merged. EOBD is the European version, and it uses the same connector and code format.
OBD III
"OBD III" is a concept in which a car would transmit fault data to roadside receivers. CARB has not adopted a mandatory remote OBD program, and its rule does not require wireless transmission.
Since then
The rules keep growing. CARB's current rule adds monitoring of the cooling system, crankcase ventilation, variable valve timing and cold-start emission strategies. Diesels must monitor particulate filters and NOx aftertreatment. The connector, the code format and the basic test modes are still the ones introduced in the 1990s, which is why a 1996 car and a new one can be read with the same scan tool.
For how the system works today, see what is OBD-II and drive cycles and readiness monitors.
OBD DashX reads and clears OBD-II trouble codes on Android with a Bluetooth ELM327 adapter.
Related codes
Sources: EPA420-F-03-042 (EPA OBD Q&A, Attachment A); CARB OBD II fact sheet; 13 CCR 1968.2; 40 CFR 86.1806; EU Directive 98/69/EC; Bosch