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,
State of Health messages are transmitted by each module on the class 2
serial data circuit about once every 2 seconds. When the module detects
no messages and a low voltage on the class 2 serial data circuit for
approximately 3 seconds, code U1300 is set and the setting of all other
class 2 serial communication DTCs is inhibited.
Conditions for Running the DTC
| • | Voltage supplied to the module is in the normal operating voltage
range of 9 to 16 volts. |
| • | The vehicle power mode 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 upon receipt of a scan tool Clear DTCs
command. |
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
. |
