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 and a low voltage on the class 2 serial
data circuit for approximately three seconds, U1300 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 9-16 volts. |
| • | The vehicle power mode--ignition switch position-- requires
serial data communication to occur. |
Conditions for Setting the DTC
| • | No valid messages are detected on the class 2 serial data circuit. |
| • | The voltage level detected on the class 2 serial data circuit
is low. |
| • | The above conditions are 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 U1300 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 U1300 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 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
. |
