Scan Tool Does Not Communicate with Class 2 Device (L18 Gas)

Scan Tool Does Not Communicate with Class 2 Device (L18 Gas)

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 trouble codes (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, DTC U1300 will be set. Refer to DTC U1300 U1300.
* When the class 2 serial data circuit is shorted to B+, DTC U1301 will be set. Refer to DTC U1301 U1301.

Test Description

The numbers below refer to the step numbers on the diagnostic table.
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. The powertrain control module communicates on the class 2 serial data circuit.
3. The following DTCs may be retrieved with a history status, but are not the cause of the present condition.

* U1300
* U1301

6. Data link connector terminal 2 and terminal 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
8. This test isolates the PCM class 2 serial data circuit.
10. If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.
11. The communication malfunction may have prevented diagnosis of the customer complaint.