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

Steps 1-6:

Steps 7-15:

Steps 16-26:

Steps 27-37:

Steps 38-50:

Steps 51-58:

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.
3. The DTC U1300 and 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 or a U1255 with a current status. This indicates that the malfunction occurred when the ignition was on.
7. The following modules, are not monitored by other modules. When one of these modules is not communicating, diagnose the malfunction using the specified procedure.
^ Memory seat module (MSM)
^ Remote control door lock receiver (RCDLR)
^ Vehicle interface unit (VIU)
8. Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
10. An open in the class 2 serial data circuit between the DLC and splice S203 will prevent the scan tool from communicating with any module. This condition will not set a DTC.
54. If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.
55. The communication malfunction may have prevented diagnosis of the customer complaint.

"For a description of the RPO Code(s) shown in this article or any of the images therein, refer to the RPO Code List found at Vehicle/Application ID". RPO Codes