Scan Tool Does Not Communicate with Class 2 Device

Scan Tool Does Not Communicate with Class 2 Device

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. Connecting a scan tool to the data link connector (DLC) allows communication with the modules for diagnostic purposes.

Diagnostic Aids

The engine will not start when there is a total loss of class 2 serial data communication while the ignition is OFF. The following conditions will cause a total loss of class 2 serial data communication:

* A class 2 serial data circuit shorted to ground.
* A class 2 serial data circuit shorted to voltage.
* An internal condition within a module or connector on the class 2 serial data circuit, that causes a short to voltage or ground to the class 2 serial data circuit.

Test Description

Step 1 - Step 11:

Step 12 - Step 19:

The numbers below refer to the step numbers on the diagnostic table.
2. A partial loss of communication in the class 2 serial data circuit uses a different procedure than a total loss of communication of the class 2 serial data circuit.
4. The following DTCs may be retrieved with a history status. These DTCs are not the cause of the present condition.

* U1300
* U1301

6. A State of Health DTC with a history status may be present along with a U1000 with a current status. This indicates that the malfunction occurred when the ignition was ON.
10. This step will isolate a wiring problem or a module malfunction.
12. This step analyzes the impact of each connected module to class 2 bus.
18. If there are no current DTCs that begin with the letter "U", the communication concern has been repaired.