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HomeFeatured ArticlesGoMechanic InformativeOBD (On Board Diagnostics) | Explained

OBD (On Board Diagnostics) | Explained

Wouldn’t it be radical, if you got to know what is wrong with your car just by pressing a few buttons? That is exactly what OBD does. OBD or On-Board Diagnostics is a revolutionary feature that allows a vehicle to diagnose and report faults codes. OBD also gives access to various subsystems within the vehicle.

The OBD system was first introduced in India in the year 2010 (limited to light-duty vehicles) and as per the recent BS6 mandate; All vehicles manufactured post-April 2020 will have to be equipped with the OBD 2 system.

What is On-Board Diagnostics?

Ever had a warning light or a “Check Engine” pop-up on the dashboard? Yes, that’s a simpler version of OBD, which illuminates to let you know that there’s something wrong with your car. The modern iteration of OBD is more sophisticated and in-depth with better insights (emissions, performance, fuel economy, ECU status) and provides troubleshooting capability for the vehicle.

OBD is a crucial tool in diagnosing, fixing and unlocking various parameters of a vehicle. A mechanic uses an OBD scanner, which enables him to read and clear DTC codes, (Diagnostics Trouble Codes) also allowing him to tweak certain complexities of the car. In this day and age of connected and smart vehicles, this system has only become more and more aware and precise.

On Board Diagnostics | The Timeline

The history of the On-Board Diagnostics system dates back to the early 1960s.

  • Volkswagen introduced an early model of On-Board Diagnostics with scanning capability in 1968.
  • Subsequently, General Motors and Datsun in the year 1978 and 1980 developed a propriety version of the OBD called ALDL (Assembly Line Diagnostics Link) to test the ECM on their cars on the production line.
  • The SAE (Society of Automobile Engineers) in the year 1988, proposed a standardised diagnostics tool to be common across every vehicle.
  • The first generation of a proper vehicle diagnostic system; OBD 1 was introduced in the year 1991.
  • 1996; OBD 2 was standardised across all vehicles in the United States with EOBD and OBD mandated in Europe and India in 2001 and 2010 respectively.

OBD 1 vs OBD 2

OBD Generation 1 OBD Generation 2
Vehicle manufacturers defined their own set of codes.
A universal set of fault codes common across all types of vehicles
Technological limitations prevented certain category
of fault codes from being detected. e.g. emissions-related codes

Strategically placed sensors triggered precise fault code detection

Every vehicle had a unique scanner that read fault codes on that particular vehicle

OBD 2 utilises universal data interface. One scanner for all vehicles

Importance of On-Board Diagnostics

  1. Diagnoses problems before it occurs
  2. Enhances vehicle occupant safety
  3. Reduces service cost and time
  4. Monitors driving behaviours, idling, air-fuel ratio etc
  5. Flexible compatibility across vehicles

The On-Board Diagnostics is a clever piece of machinery with sensors rigged all over the vital components in a car. Whenever a malfunction is detected, a DTC (Diagnostics Trouble Codes) is generated in the OBD subsystem. These codes can be either generic or unique as defined by the vehicle manufacturer. A mechanic; using an OBD scanner checks these fault codes and pinpoints the root cause of the problem.

Variations of DTC or Fault Codes:

  • PXXXX: Indicates a problem in the powertrain.
  • BXXXX: Indicates a problem in the body
  • CXXXX: Indicates a problem in the chassis
  • UXXXX: Indicates a problem in the network

More Information on OBD2 Trouble Codes

Is My Car OBD Compliant?

In a modern car, the OBD 2 port is typically located in the car cabin, near the driver side. You can find the port access at the underside of the dashboard or adjacent to the fuse box. Beware though, tinkering with the On-Board Diagnostics requires special equipment (scanner, data logger) and training, there are many things that can go wrong so, always exercise caution. Drive in to your nearest GoMechanic workshop for a FREE scanning and diagnostics session if you are that curious.

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Akshat Ajeya
Akshat Ajeya
Lead, Content & Creatives at GoMechanic | Automobile Scale Model Collector | DIY guy | Consumer of many foods | CVT is not that bad


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