Circuit Description

Modules connected to class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged between modules. In addition to this, state of health messages are transmitted by each module on class 2 serial data circuit about once every 2 seconds. When module detects no messages and a low voltage on class 2 serial data circuit for approximately 3 seconds, code U1300 is set and setting of all other class 2 serial communication DTCs is inhibited.

DTC U1300 sets when:

• No valid messages are detected on class 2 serial data circuit.
• Voltage level detected on class 2 serial data circuit is low.
• Conditions are met for approximately 3 seconds.

When DTC sets, module inhibits setting of all other class 2 serial communication DTCs. Module uses default values for all parameters received on class 2 serial data circuit.

A current U1300 will clear when a valid class 2 message is detected on class 2 serial data circuit or at end of current ignition cycle. A history U1300 can be cleared with scan tool.