User manual

60
Troubleshooting Communication Problems
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 the table below.
Figure A-1
Contact designation for vehicle connector mating end view
Use the following voltage tests at the DLC to help determine the reason that a vehicle does not
communicate. Always use a high-impedance digital voltmeter.
z To test the DLC:
1. Ground—Connect the voltmeter positive (+) lead to the ground terminal in the diagnostic
connector. Connect the negative (–) lead directly to the battery negative (–) terminal.
Do not connect the voltmeter negative lead to an engine or chassis ground. This test
measures the voltage drop across the ground side of the DLC. An ideal system ground should
have a voltage drop of 0.1 V or less. An open ground can keep a fuel injected engine from
starting. A high-resistance, or “dirty”, ground can cause overall poor operation.
2. Battery Voltage—Connect the voltmeter positive (+) lead to the battery voltage terminal at the
diagnostic connector. Connect the negative (–) lead to the battery ground terminal.
Contact General allocation
1 Discretionary
1)
2 Bus positive line of SAE J1850
2)
3 Discretionary
1)
4 Chassis ground, (See Note below)
5 Signal ground, (See Note below)
6 CAN_H line of ISO 15765-4 2)
7 K-LINE of ISO 9141-2 and ISO 14230-4
2)
8 Discretionary
1)
9 Discretionary
1)
10 Bus negative line of SAE J1850
2)
11 Discretionary
1)
12 Discretionary
1)
13 Discretionary
1)
14 CAN_L line of ISO 15765-4
2)
15 L-LINE of ISO 9141-2 and ISO 14230-4
2)
16 Permanent positive voltage
1)
Assignment of contacts 1, 3, 8, 9, 11, 12 and 13 in the vehicle connector
is left to the discretion of the vehicle manufacturer.
2)
Note, for contacts 2, 6, 7, 10, 14 and 15 the related diagnostic
communication assignments are shown. These contacts may also be used
for alternate assignments in the vehicle connector.
21 3 4 5 6 7 8
109 11 12 13 14 15 16