Circuit Description
The class 2 serial data line communicates information between
the modules. Each module connected to the serial data line is assigned a recognition
code, or address. This code is used in order to identify which modules
are communicating. Modules communicate with each other by periodically
sending state of health (SOH) messages. When the ignition switch is
in RUN, each module that is communicating on the serial data line sends
an SOH message every 2 seconds. This ensures that the system
is operating properly. The module also monitors the serial data line
for short to ground. If the module detects a short to ground for more
than 3.0 seconds, the module stores the class 2 Bus Shorted
to ground DTC U1300.
Conditions for Running the DTC
| • | Diagnostic trouble code B1327 does not have a current status. |
| • | The vehicle power mode (ignition switch position) requires serial
data communication to occur. |
Conditions for Setting the DTC
| • | No valid messages are detected on the class 2 serial data circuit. |
| • | The voltage level detected on the class 2 serial data circuit
is low. |
| • | The above conditions are met for approximately three seconds. |
Action Taken When the DTC Sets
| • | DTC U1300 is stored in the memory module. |
| • | The module inhibits the setting of all other class 2 DTCs. |
| • | The module uses the default values for any information needed
from the other modules on the class 2 serial data line. |
| • | This DTC does not cause a driver warning message to appear. |
Conditions for Clearing the DTC
| • | This DTC clears (status changes from current to history) when
the module detects the class 2 serial data line is not shorted to ground. |
| • | A history DTC clears after 50 consecutive ignition cycles
if the conditions for setting the DTC are no longer present. |
| • | Current and history DTCs may be cleared manually by using a scan
tool. |
Diagnostic Aids
