Circuit Description
Modules connected to the Class 2 data link monitor the link for serial
data communications during normal vehicle operation. Operating information
and commands are exchanged among the modules. Also, Node Alive (State Of
Health) messages are transmitted by each module on the data link about once
every two seconds. When the module detects no messages and a low voltage
on the data link for approximately three seconds, U1300 is set and the setting
of all other communication DTCs are inhibited.
Conditions for Setting the DTC
| • | Voltage supplied to the module is in the normal operating range
(approximately 9-16 volts). |
| • | No valid Class 2 messages are detected on the data link. |
| • | The voltage level detected on the data link is low. |
| • | The above conditions are all met simultaneously for three seconds. |
Conditions for Clearing the DTC
| • | A current U1300 will clear when a valid Class 2 message is detected
on the data link or at the end of the current ignition cycle. |
| • | A history U1300 will clear upon receipt of a scan tool "Clear
DTC's" command. |
Diagnostic Aids
| • | This DTC cannot be retrieved with a current status. Diagnosis
of a current U1300 is accomplished via the symptom, Scan Tool will not Communicate
with the Class 2 serial data line. |
| • | An intermittent condition is likely to be caused by a short to
ground on the Class 2 serial data line. |
