What is OBD 2 / OBD II? A Guide to On-Board Diagnostics

You may have come across the terms “OBD” or “OBDII” when reading about connected vehicles and the Geotab GO device. These features are part of a car’s on-board computers and have a history not many know about. Read this post for an overview of OBDII and a timeline of its development.

What is an OBD (on-board diagnostics)?

On-board diagnostics (OBD) refers to the automotive electronic system that provides vehicle self-diagnosis and reporting capabilities for repair technicians. An OBD gives technicians access to subsystem information for the purpose of performance monitoring and analysing repair needs.

OBD is the standard protocol used across most light-duty vehicles to retrieve vehicle diagnostic information. Information is generated by engine control units (ECUs or engine control modules) within a vehicle — essentially the vehicle's onboard computers.

Why is OBD so important?

OBD is an important part of telematics and fleet management, making it possible to measure and manage vehicle health and driving.

Thanks to the OBD, fleets can:

• Track wear trends and identify which vehicle parts are degrading faster than others
• Diagnose vehicle problems before they occur, enabling proactive rather than reactive maintenance
• Measure driving behaviour, speed, idling time, and fuel consumption in real time

Where is the OBD 2 port located?

In a typical passenger vehicle, you can find the OBD 2 port on the underside of the dashboard on the driver's side of the car — usually within 60 cm of the steering wheel. Depending on the vehicle type, the port could have a 16-pin, 6-pin or 9-pin configuration.

If you want to connect a Geotab GO device to your OBD port, read How to install a Geotab GO vehicle tracking device.

What is an OBD scanner?

An OBD scanner (also called an OBD reader or OBD diagnostic tool) is a device that plugs into a vehicle's OBD 2 port and reads the data the vehicle's computer is generating. Consumer OBD scanners display fault codes so drivers can diagnose issues at home. Professional OBD scanners used by mechanics decode the full range of diagnostic trouble codes (DTCs) to pinpoint specific faults quickly.

For fleet operators in the Philippines and Malaysia, a telematics device like the Geotab GO acts as a permanently connected OBD scanner — continuously reading vehicle data and streaming it to a fleet management platform in real time, rather than requiring manual plug-in checks.

What's the difference between OBD and OBD 2?

OBD 2 (also written as OBD II or OBD-II) is simply the second generation of the original OBD, or OBD I. The OBD I was initially externally connected to the console of a car, while OBD 2 is now integrated within the vehicle itself. The original OBD was used until OBD 2 was introduced in the early 1990s.

To learn more about the value of the OBD port, read this white paper: Preserving privacy and security in the connected vehicle: The OBD port on the road ahead.

History of OBD 2

The history of on-board diagnostics goes back to the 1960s. Several organisations set the groundwork for the standard, including the California Air Resources Board (CARB), the Society of Automotive Engineers (SAE), the International Organization for Standardization (ISO) and the Environmental Protection Agency (EPA).
 

Before standardisation, manufacturers were creating their own systems — each with their own connector type, electronic interface, and custom fault codes. OBD 2 changed all of that.

Highlights in OBD history:

1968 — The first OBD computer system with scanning capability was introduced by Volkswagen.

1978 — Datsun introduced a simple OBD system with limited non-standardized capabilities.

1979 — The Society of Automotive Engineers (SAE) recommends a standardized diagnostic connector and set of diagnostic test signals.

1980 — GM introduced a proprietary interface and protocol capable of providing engine diagnostics through an RS-232 interface or more simply, by flashing the Check Engine Light.

1988 — Standardization of on-board diagnostics came in the late 1980s after the 1988 SAE recommendation that called for a standard connector and set of diagnostics.

1991 — The state of California required all vehicles to have some form of basic on-board diagnostics. This is referred to as OBD I.

1994 — The state of California mandated that all vehicles sold in the state starting in 1996 must have OBD as recommended by SAE — now referred to as OBD2 (OBDII). This stems from the desire to perform across the board emissions testing. OBD2 included a series of standardized diagnostic trouble codes (DTCs) Open in new window.

1996 — OBD-II becomes mandatory for all cars manufactured in the United States.

2001 — EOBD (European version of OBD) becomes mandatory for all gasoline vehicles in the European Union (EU).

2003 — EOBD becomes mandatory for all diesel vehicles in the EU.

2008 — Starting in 2008, all vehicles in the US are required to implement OBD2 through a Controller Area Network as specified by ISO 15765-4.

What data can be accessed from the OBD 2?

The OBD 2 provides access to status information and Diagnostic Trouble Codes (DTCs) for:

• Powertrain (Engine and transmission)
• Emission Control Systems

Additionally, you can access the following vehicle information via the OBD 2 port:

• Vehicle Identification Number (VIN)
• Calibration Identification Number
• Ignition counter
• Emissions Control System counters

When a car is taken to a shop for service, a mechanic connects to the OBD port with an OBD scanner, reads the trouble codes, and identifies the problem — allowing accurate diagnosis and faster repairs.

Examples

Mode 1 (Vehicle Information):

• Pid 12 — Engine RPM
• Pid 13 — Vehicle Speed

Mode 3 (Trouble Codes: P = Powertrain, C = Chassis, B = Body, U = Network):

• P0201 — Injector circuit malfunction – Cylinder 1
• P0217 — Engine over temperature condition
• P0219 — Engine overspeed condition
• C0128 — Low brake fluid circuit
• C0710 — Steering position malfunction
• B1671 — Battery Module Voltage Out Of Range
• U2021 — Invalid/ fault data received

For a full reference, see this list of standard diagnostic trouble codes Open in new window.

OBD and telematics

The OBD 2 port allows telematics devices to silently process information such as engine revolutions, vehicle speed, fault codes, fuel usage, and more. The telematics device uses this data to determine trip start and finish, over-revving, speeding, excessive idling, and fuel consumption — all uploaded to a software platform so fleet managers can monitor vehicle use and performance.

With the multitude of OBD protocols, not all telematics solutions are designed to work with all vehicle types. Geotab overcomes this by translating diagnostic codes from different makes, models, and even electric vehicles.
 

In fleet-heavy markets like Philippines and Malaysia — where Toyota HiAce vans, Mitsubishi Strada pickups, and Isuzu trucks are common — OBD 2 compatibility across makes and models is critical. Geotab's GO device supports OBD 2 and proprietary manufacturer protocols, ensuring accurate data collection regardless of vehicle brand.

With the OBD 2 port, a fleet tracking solution can be connected to your vehicle quickly and easily — in the case of Geotab, in under five minutes. If your vehicle doesn't have a standard OBD 2 port, an adapter can be used instead. No special tools or professional installer required.

What is WWH-OBD?

WWH-OBD stands for World Wide Harmonized on-board diagnostics. It is an international standard used for vehicle diagnostics, implemented by the United Nations as part of the Global Technical Regulations (GTR) mandate, which includes vehicle data monitoring such as emissions output and engine fault codes.

Advantages of WWH-OBD

Here’s a look at the benefits of moving toward WWH in more technical terms:

Access to more data types

Currently, the OBD 2 PIDs used in Mode 1 are only one byte long, meaning up to 255 unique data types are available. WWH-OBD expands this, allowing for more available data types and future expansion.

More detailed fault data

OBD 2 uses a two-byte diagnostic trouble code (DTC) to indicate a fault — for example, P0070 indicates Ambient Air Temperature Sensor "A" has a general electrical failure.

Unified Diagnostic Services (UDS) expands this into a 3-byte DTC, where the third byte indicates the failure "mode." Previously on OBD 2, five separate fault codes were needed to describe sensor states:

• P0070 Ambient Air Temperature Sensor Circuit
• P0071 Ambient Air Temperature Sensor Range/Performance
• P0072 Ambient Air Temperature Sensor Circuit Low Input
• P0073 Ambient Air Temperature Sensor Circuit High Input
• P0074 Ambient Air Temperature Sensor Circuit Intermittent

With WWH, these consolidate into a single P0070 code with five failure modes in the third byte — for example, P0071 becomes P0070-1C. WWH also provides severity, class, and fault status — indicating how urgently a fault needs attention and whether it is pending, confirmed, or resolved.

Geotab supports WWH-OBD

Geotab has already implemented the WWH protocol into our firmware. Our complex protocol detection system safely examines what is available on the vehicle to determine whether OBD 2 or WWH is available — and in some cases, both are.
 

When new information becomes available through either OBD 2 or WWH — a new PID, fault data, or protocol — Geotab adds it into firmware and immediately delivers the update over the cloud. Customers always get the greatest benefit from their devices without manual intervention.

Growth beyond OBD 2

OBD 2 contains 10 standard modes to achieve the required diagnostic information for emission standards. Over the years, those 10 modes have not been enough.

Various UDS modes have developed since OBD 2 was implemented — each vehicle manufacturer uses proprietary PIDs and implements them via extra UDS modes. Information not required under OBD 2 (such as odometer readings and seatbelt use) became available through UDS instead.

UDS contains upwards of 20 additional modes beyond OBD 2's 10 standard modes. WWH-OBD looks to incorporate UDS with OBD 2 to enrich diagnostic data while maintaining a standardised process.

Conclusion

OBD 2 is the backbone of modern vehicle diagnostics — and of fleet management. Whether a mechanic is reading fault codes with a handheld OBD scanner or a fleet manager is monitoring hundreds of vehicles through a telematics platform in the Philippines and Malaysia, it all starts at the OBD 2 port. As vehicle data standards evolve toward WWH-OBD, fleets that adopt compatible telematics solutions today will be best placed to capture richer diagnostic insights tomorrow.