OBD II Explained

The vehicle manufacturers have different interpretations of OBD-II requirements. This makes it rather difficult to define a specific approach to DLC (Diagnostic Link Connector) problem diagnosis. For example, some manufacturers use the SAE J1850 BUS+ line but not the BUS-, while others use the ISO 9141 K-LINE, but not the L-LINE. See Table A-1: ‘General contact allocations’ below.

Ford has used 3 lines, the J1850 lines for powertrain tests, and the ISO 9141 line for the non-powertrain tests. There are also vehicles with no ground at pin 4. In addition, a pin location that is wired, does not necessarily mean it is wired based on the OBD-II requirements.

Table A-1 General contact allocationsContact
General allocationTable

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