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 module 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 Running the DTC
| • | Voltage supplied to the modules are in the normal operating voltage
range (approximately 9-16 volts). |
| • | The module operation requires serial data communication to occur. |
Conditions for Setting the DTC
| • | 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. |
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 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 after completion of 100 ignition switch
ON/OFF cycles with no repeated malfunction. |
Diagnostic Aids
