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 2 seconds.
When a module detects no messages on the class 2 serial data circuit
for approximately 3 seconds, with no low or high voltage detected,
U1305 is set. 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 9-16 volts). |
| • | The module operation or 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 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 after 100 ignition switch ON/OFF cycles
with no repeated malfunction. |
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
. |
