Circuit Description

The Class-II serial data line is used to communicate information between modules. Each module connected to the serial data line is assigned its own recognition code (address). This DTC is used to identify which modules are communicating. Modules communicate with each other by periodically sending State Of Health (SOH) messages.

When ignition switch is in RUN position, each module communicating on the serial data line sends a SOH message every 2 seconds (one second for PCM) to ensure that system is operating properly.

This module monitors serial data line for a short to ground or voltage. If module detects a short to ground for longer than 3 seconds, no communication will be established between this module and other modules, setting DTC U1300.

Conditions of setting DTC:

• DTC U1300 only sets if DTC B1327, B1328, B1982 or B1983 is not current in module memory.
• The module detects that the Class-II serial data line is shorted to ground for at least 3 seconds.