Circuit Description
Modules connected to the class 2 serial data link monitor the link 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 link about once every 2 seconds. When the module detects no messages
and a high voltage on the class 2 serial data link for approximately 3 seconds,
U1301 is set and the setting of all other class 2 serial communication DTCs
is inhibited.
Conditions for Setting the DTC
| • | Voltage supplied to the module is in the normal operating voltage
range (approximately 9-16 volts). |
| • | No valid class 2 messages are detected on the class 2 serial data
link is high. |
| • | The voltage level detected on the class 2 serial data link is
high |
| • | The above conditions are all met simultaneously for three seconds. |
Action Taken When the DTC Sets
| • | The module inhibits the setting of all other class 2 DTCs. |
| • | DTC U1301 is set by the module. |
Conditions for Clearing the DTC
| • | A current U1301 will clear when a valid class 2 message is detected
on the class 2 serial data link or at the end of the current ignition cycle. |
| • | A history U1301 will clear upon receipt of a scan tool Clear DTCs
command. |
Diagnostic Aids
This DTC cannot be retrieved with a current status. Diagnosis of a current
U1301 is accomplished via the symptom. The scan tool will not communicate
with a class 2 device. An intermittent condition is likely to be caused by
a short to voltage on the class 2 serial data link.
