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
one of the following conditions on the class 2 serial data circuit
for approximately 3 seconds, the setting of all other class 2
serial communication DTCs is inhibited and a DTC will set.
DTC
| Condition
|
U1300
| Low voltage on the Class 2 serial data circuit.
|
U1301
| High voltage
on the Class 2 serial data circuit.
|
U1305
| Short on the Class 2 serial data circuit, either high or low.
|
Conditions for Running the DTCs
| • | Voltage supplied to the module is in the normal operating voltage
range. |
| • | The vehicle power mode requires serial data communication to occur. |
Conditions for Setting the DTCs
| • | No valid messages are detected on the class 2 serial data
circuit. |
| • | The voltage level detected on the class 2 serial data circuit
is under one of the following conditions: |
| • | The above conditions are met for approximately 3 seconds. |
Action Taken When the DTCs 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 DTCs
| • | Current DTCs 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. |
| • | History DTCs will clear upon receipt of a scan tool Clear DTCs
command. |
Diagnostic Aids
| • | An intermittent condition is likely to be caused by a short or
an open 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
. |
