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 circuit about once every two seconds. When the body
control module (BCM) and radio receiver detects no messages and a high voltage
on the Class 2 serial data circuit for approximately three seconds, U1301
is set and the setting of all other communication DTCs is inhibited.
Conditions for Setting the DTC
| • | Voltage supplied to the modules are in the normal operating voltage
range (approximately 9-16 volts). |
| • | No valid Class 2 messages are detected on the Class 2 serial data
circuit. |
| • | The voltage level detected on the Class 2 serial data circuit
is high. |
| • | The above conditions are all met for approximately three seconds. |
Conditions for Clearing the DTC
| • | A current U1301 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 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, Scan Tool Will Not Communicate
With Class 2 Data Line. |
| • | An intermittent condition is likely to be caused by a short to
voltage on the Class 2 serial data circuit. Use the Scan Tool Will Not Communicate
With Class 2 Data Line procedure to isolate the condition. |
