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 on the class 2 serial data circuit for approximately three seconds,
U1305 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 above condition is 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 U1305 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 U1305 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
ground or 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
. |
