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 messages are transmitted by each module on the class 2
serial data circuit about once every 2 seconds. When the module
detects the class 2 serial data circuit shorted, the setting of all
other class 2 serial communication DTCs is inhibited and a U1300,
U1301, or a U1305 DTC will set.
Conditions for Running the DTC
| • | Voltage supplied to the module is within the normal operating
voltage range. |
| • | The vehicle power mode 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 class 2 serial data circuit is shorted to ground or
voltage. |
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 DTC clears when the malfunction is no longer present. |
| • | A history DTC clears when the module ignition cycle counter reaches
the reset threshold, without a repeat of the malfunction. |
Diagnostic Aids
| • | This DTC cannot be retrieved with a current status. The diagnosis
of U1305 is accomplished via the symptom, Scan Tool Does Not Communicate
with a Class 2 Device. Refer to Scan Tool Does Not Communicate
with Class 2 Device . |
| • | An intermittent condition is likely to be caused by a short to
ground or voltage on the class 2 serial data circuit. Use Scan Tool
Does Not Communicate with Class 2 Device to isolate an intermittent
condition. |
