INSPECTION PROCEDURE 1: Communication with Scan Tool Is Not Possible (Comunication with All Systems Is Not Possible)

CIRCUIT OPERATION
A battery positive voltage is applied on the data link connector power terminal (terminal No. 16). The ground terminals (terminals No. 4, No. 5) are grounded to the vehicle body.
COMMENT
The cause is probably a defect in power supply system (including ground) for the on-board diagnostic test mode line.
TROUBLESHOOTING HINTS (The most likely causes for this case: )
Malfunction of the data link connector.
Damaged harness wire.