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,
State of Health messages are transmitted by each module on the class 2
serial data circuit about once every 2 seconds. When the module detects
no messages on the class 2 serial data circuit for approximately 3 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 of 9 to 16 volts. |
| • | 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 above condition is met for approximately 3 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
. |
