EOBD fulfills a European Union requirement for car emission diagnostics.
The European On-Board Diagnostics (EOBD) protocols are diagnostics languages for EOBD automobile engine-management systems. These systems are mandatory throughout the European Union for managing engine emissions. They are a requirement for all petrol-engined cars weighing less than 2.5 tonnes sold since January 1st 2001 and diesel cars sold since January 1st 2004. The requirements include a socket that gives access to monitoring systems called an EOBD Diagnostic Connector. There a five EOBD protocols apart from the specification for the connector.
EOBD Diagnostic Connector
The connector is known by the abbreviation DLC, which stands for Data Link Connector and is also designated by the protocol code J1962. The DLC has 16 pins in two rows of eight. Not all pins have a purpose specified in the EOBD protocol, but are left for use by vendor implementations. Pin 2 is called the J1850 Bus+, which is where the five-language protocol presents data.
Variable Pulse Width
J1850 VPW is a language specification to carry data over the J1850 pin on the DLC. Apart from pin 2, VPW uses pins 4 and 16 for battery power and pin 5 for the signal ground. The language protocols can be duplex, having an in and out channel for data communications, but VPW only uses one channel over which data passes in both directions. This protocol was preferred by General Motors and Chrysler.
Pulse Width Modulation
J1850 PWM uses pins 2 and 10 for two-way communication. Pins 4 and 16 are used for battery power and pin 5 is used for the signal ground. This protocol was preferred by Ford for its fuel engine cars.
ISO
ISO stands for International Standards Organization. The full name of this protocol is ISO 9141-2. Most European and Asian Manufacturers used this standard. It does not use the J1850 bus to pass data. Instead it sends data over pin 7 and optionally also pin 15. These are called the "K-line" and the "L-line." As with other EOBD protocols, battery power passes over pins 4 and 16 and pin 5 is used for the signal ground.
KWP2000
ISO 14320 KWP2000 is another standard used by European and Asian manufacturers. KWP stands for the Keyword Protocol. The pin usage of KWP2000 is the same as that used for ISO 9141-2.
Controller Area Network
The ISO 15765 CAN standard has been mandatory since 2008 for all EOBD implementations. The CAN Bus was developed by Bosch in the mid 1990s. It was implemented in many car models, but was not approved for EOBD until 2003. Until then, the other four approved standards had to be used by car manufacturers. This gave slower performance on reading diagnostic data. The CAN Bus connects computer-controlled components in a car and so already provided a path for diagnostics reporting and delivers data faster than the other standards. CAN data is accessed over pins 6 and 14 on the DLC. Pins 4 and 16 carry battery power and pin 5 gives the signal ground.
Tags: battery power, signal ground, EOBD protocols, data over, Diagnostic Connector, EOBD Diagnostic, EOBD Diagnostic Connector