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Experts in car diagnostics since 2001
  Home Articles OBDII and EOBD questions

The EOBD / OBDII 16-pin diagnostic connector (DLC)

Where is the connector?

The EOBD connector is required by the Directive to be located within the passenger compartment of the car, within reach of the driver's seat. Tools should not be required to reveal the connector, but it may have a removeable cover over it.

What does the connector look like?

The connector has the following shape:
Diagnostic Connector

Which pins contacts should be present on the connector?

Different pins on the connector are used by different manufacturers. There are 5 pinout combinations within the standard, each of which uses a specific communications protocol. These are listed below:
Protocol Connector pins used
J1850 VPW 2, 4, 5, and 16, but not 10
ISO 9141-2 4, 5, 7, 15 (see below) and 16
J1850 PWM 2, 4, 5, 10 and 16
(ISO 14230)
4, 5, 7, 15 (see below) and 16
CAN (Controller Area Network) 4, 5, 6, 14 and 16
Note: For ISO/KWP2000 communications, pin 15 (L-line) is not always required. Pin 15 was used on earlier ISO/KWP2000 cars to "wake-up" the ECU before communication could begin on pin 7 (K-Line). Later cars tend to communicate using only pin 7 (K-Line).

Rover and MG cars: We have noticed that many Rover and MG models do not have pin 5 (Signal Ground). This can prevent some diagnostic tools from 'powering up' where they use pin 5 as the ground for the circuitry. All the tools we sell now are deliberately shorted between pins 4 and 5 to combat this problem.

What are each of the pins used for?

The pins are used as follows:
Pin Use
2 J1850 Bus+
4 Chassis Ground
5 Signal Ground
6 CAN High (J-2284)
7 ISO 9141-2 K Line and ISO/DIS 14230-4
10 J1850 Bus
14 CAN Low (J-2284)
15 ISO 9141-2 L Line and ISO/DIS 14230-4
16 Battery power
Additional pins may be wired on your car - these may be used by manufacturers for other purposes.

Which protocol is used by each manufacturer?

As a rough guide, the protocols are generally found on cars from the following manufacturers:
Protocol Manufacturers
J1850 VPW
General Motors, Chrysler
J1850 PWM
Ford models to 2003 with EEC-V engine management system, this includes:
Ford Cougar (all UK models), Ford Puma (1.6 and 1.7), Ford Fiesta Zetec models to 2003, Ford Mondeo Zetec models to 2003, Ford Focus to 2003
(and some of the newer Ford-based Jaguars, e.g. S-Type)
Most European and Asian manufacturers, e.g.
Alfa Romeo, Audi, BMW, Citroen, Fiat, Honda, Hyundai, Jaguar (X300, XK series and X-Type), Jeep, Kia, Land Rover, Mazda, Mercedes, Mitsubishi, Nissan, Peugeot, Renault, Saab, Skoda, Subaru, Toyota, Vauxhall, Volkswagen (VW), Volvo
Ford 2004+ Fiesta, Fusion, Focus models, 2007+ Mondeo
Mazda RX-8
Vauxhall Vectra 2003+ model

Most new models from approx. 2004 - CAN must be used for EOBD engine diagnostics by all manufacturers by 2008
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