Circuit Description
Modules connected to the class 2 serial data circuit monitor for serial
data communications during normal vehicle operation. Operating information
and commands are exchanged among the modules. In addition to this,
Node Alive (State of Health) messages are transmitted by each module
on the class 2 serial data circuit about once every two seconds. When
the module detects no messages and a high voltage on the Class 2 serial
data link for approximately three seconds, U1301 is set and the setting
of all other class 2 serial communication DTCs is inhibited.
Conditions for Running the DTC
| • | Voltage supplied to the module
is in the normal operating voltage range (approximately 9 to 16 volts). |
| • | The vehicle power mode (ignition switch position) requires
serial data communication to occur. |
Conditions for Setting the DTC
| • | No valid class 2 messages are
detected on the class 2 serial data circuit. |
| • | The
voltage level detected on the class 2 serial data circuit is high. |
| • | The above conditions are met for approximately three seconds. |
Action Taken When the DTC Sets
| • | The module inhibits the setting
of all other class 2 DTCs. |
| • | The module uses default
values for all parameters received on the class 2 serial data circuit. |
Conditions for Clearing the DTC
| • | A current U1301 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
U1301 will clear upon receipt of a scan tool Clear DTCs command. |
Diagnostic Aids
| • | An intermittent condition is likely
to be caused by a short to voltage on the class 2 serial data circuit. Use
the Scan Tool Does Not Communicate with a Class 2 Device procedure in
order to isolate an intermittent condition. Refer to
Scan Tool Does Not Communicate with Class 2 Device |
