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 DLC allows communication with the modules for diagnostic purposes. DTCs may be set due to this symptom and during this diagnostic procedure. Complete the diagnostic procedure in order to ensure all the DTCs are diagnosed and cleared from memory.

Diagnostic Aids

When the class 2 serial data circuit:

* Is shorted to ground
* Is shorted to voltage
* Opens

The following DTCs may set:

* U1300
* U1301
* U1305

Refer to DTC U1300, U1301, or U1305 U1300.

Test Description

The numbers below refer to the step numbers on the diagnostic table.
2. The powertrain control module (PCM) communicates on the class 2 serial data circuit with the L18/8.1 engine. The transmission control module (TCM) communicates of the class 2 serial data circuit with the LG5/7.2 engine.
3. The following DTCs may be retrieved with a history status, but are not the cause of the present condition.

* U1300
* U1301
* U1305

5. DLC terminal 2 and terminal 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
7. This test isolates either the PCM or TCM class 2 serial data circuit, depending on RPO.
9. If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.
10. The communication malfunction may have prevented diagnosis of the customer complaint.