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.

Diagnostic Aids

The engine will not start when there is a total malfunction of the class 2 serial data circuit while the engine is not running.

Test Description

2. A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit.
3. DTCs U1300 and/or U1301 may be retrieved with a history status. These DTCs are not the cause of the present condition.
6. A state of health DTC with a history status may be present along with a U1000 having a current status. This indicates the malfunction occurred when the ignition was on.
7. Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
9. A poor connection at connector C1 terminal D2 would cause this condition but may not set a DTC.
10. An open in the class 2 serial data circuit between the DLC and the left IP junction block connector will prevent the scan tool from communicating with any module. This condition may not set a DTC.
11. This test isolates the serial data circuit within the left IP junction block.
12. This test isolates the BCM class 2 serial data circuit.
13. This test isolates the SDM class 2 serial data circuit
14. This test isolates the EBCM class 2 serial data circuit
15. This test isolates the PCM class 2 serial data circuit
18. If there are no current DTCs that begin with a U, the communication malfunction has been repaired.
19. The communication malfunction may have prevented diagnosis of the customer complaint.