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 seconds, the module
stores the class 2 serial data circuit shorted to ground DTC U1300.
Conditions for Running the DTC
| • | The following diagnostic trouble codes do not have a current status: |
| • | The vehicle power mode 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 3 seconds. |
Action Taken When the DTC Sets
| • | DTC U1300 is stored in the module memory. |
| • | 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. |
Conditions for Clearing the DTC
| • | A current DTC will clear when a valid class 2 message is
detected on the class 2 serial data circuit or at the end of the current
ignition cycle. |
| • | A history DTC clears after 50 consecutive ignition cycles
without a repeat of the malfunction. |
Diagnostic Aids
