What is OBD II?
Automotive Diagnostics, Fleet Tracking, Green Technology, and Vehicle Insurance all use OBD II.
OBD II has been mandatory on all vehicles in North America since 1996 and in Europe since 2004. You can use OBD II to read key vehicle information and determine a vehicle’s position, its fuel efficiency, and even monitor driver behavior.
OBD II is an open standard. That means that any company with the proper software and the right external circuitry can read OBD II information.
You can read more about the history of OBD II on our page A brief history of OBD II.
What are OBD II Protocols?
The OBD II standard is implemented electrically in five different ways. Each of these electrical communication methods is called a protocol. Some protocols use two wires, some only one.
The five acceptable OBD II protocols are:
- ISO 9141-2
- KWP 2000-4
- SAE J1850 PWM ( also called Ford SCP)
- SAE J1850 VPW (also called GM Class 2)
- ISO 15765-4 (also called CAN 11-bit & 29-bit)
In North America all cars from 2008 onward must use the CAN protocol (ISO 15765-4).
To connect to vehicle using OBD II you use the J1962 connector, this must be present in every car within one meter of the steering wheel.
The J1962 connector shows which OBD II protocol is implemented by a vehicle. This connector (shown below) is often located under the steering wheel on the driver’s side of the vehicle.
The numbers in picture represent the 16 pins of the J1962 connector. The following J1962 connections are dependent on the protocol(s) in use by the vehicle:
- Pin 2 and pin 10 are used for both J1850 (PWM or VPW) protocols
- Pin 7 and pin 15 s used for ISO 9141-2 and ISO 14230 (KWP 2000) communications. These pins are also known and the K-Line and the L-Line (however the L-line may or may not be present for these protocols).
- Pin 6 and pin 14 are present for CAN (ISO 15765-4) protocol.
Pin 16 is Battery Voltage and Pins 4 & 5 are Ground. By checking which pins are implemented in a vehicle it may be possible to determine which OBD II protocol is in use.
OBD II Modes
Once you have connected to the car using one of the five OBD II protocols described above you can use the ten OBD II modes to read information from the vehicle.
Mode 1, lets you read valuable vehicle information such as the “Engine RPM”, “Vehicle Speed”, “Fuel Level”, and “Run Time Since Engine Start”. You can use this information to track fuel usage and monitor driver behavior.
Use Modes 3 and 4 to diagnose vehicle problems. Mode 3 allows you to read all Diagnostic Trouble Codes (DTCs) that are present on the vehicle. Mode 4 lets you Clear DTCs which turns off the Malfunction Indicator Lamp (MIL).
Using Mode 9, you can read the Vehicle Identification Number. This allows you to determine the make, model and year of a vehicle.
Modes Supported by the OBD II Protocol Stack
| Mode 1 | Get current data (RPM, Speed, Fuel Level, Engine Load, etc) |
| Mode 2 | Get data that existed at time of last DTC |
| Mode 3 | Get Diagnostic Trouble Codes (DTCs) |
| Mode 4 | Clear Diagnostic Trouble Codes (DTCs) |
| Mode 5 | Oxygen sensor monitoring test |
| Mode 6 | On-board monitoring, other tests |
| Mode 7 | Pending Diagnostic Trouble Codes |
| Mode 8 | Control operation of on-board system |
| Mode 9 | Request Vehicle information (eg VIN) |
| Mode 10 | Permanent Diagnostic Trouble Codes |
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