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 serial data messages and a low voltage on the class 2
serial data circuit for approximately 3 seconds, U1300 is set. The
setting of all other class 2 serial communication DTCs is inhibited.
Conditions for Running the DTC
| • | Voltage supplied to the vehicle modules is in the normal operating
voltage range (approximately 9-16 volts). |
| • | The module operation or 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 after 100 ignition switch ON/OFF cycles
with no repeat of the malfunction. |
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
. |
